/ Thesaurus O: Synonyms for Letter O A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Verb o.d. o.k. obey obfuscate object objectify objurgate obligate oblige obliterate obnubilate obscure observe obsess obsolesce obstinate obstipate obstruct obtain obtrude obtrude upon obtund obturate obviate occasion occidentalise occidentalize occlude occult occupy occur odorize odourise off offend offer offer up officer officialise officialize officiate offload offsaddle offset ogle oil oink okay omen omit one-step ooh ooze ooze out ooze through opacify opalesce opalise opalize open open fire open up operate operate on opine oppose oppress oppugn opsonize opt opt out optimise optimize orate orb orbit orchestrate ordain order ordinate organise organize orient orientalise orientalize orientate originate originate in ornament orphan oscillate osculate ossify ostentate ostracise ostracize oust out out-herod out in outbalance outbid outbrave outcall outclass outcrop outcry outdistance outdo outdraw outface outfight outfit outflank outfox outgeneral outgo outgrow outguess outlast outlaw outline outlive outmaneuver outmanoeuvre outmarch outmatch outmode outnumber outpace outperform outplay outpoint output outrage outrange outrank outride outrival outroar outrun outsail outscore outsell outshine outshout outsmart outsource outspan outstare outstay outstrip outvie outvote outwear outweigh outwit oven broil ovenbake over-correct over-refine overachieve overact overarch overawe overbalance overbear overbid overboil overburden overcapitalise overcapitalize overcast overcharge overclothe overcloud overcome overcompensate overcook overcrop overcrowd overcultivate overdo overdose overdramatise overdramatize overdraw overdress overdrive overeat overemphasise overemphasize overestimate overexert overexert oneself overexploit overexpose overextend overfatigue overfeed overfill overflow overfly overgeneralise overgeneralize overgorge overgrow overhang overhaul overhear overheat overindulge overjoy overlap overlay overleap overlie overload overlook overmaster overpay overplay overpopulate overpower overpraise overprice overprint overproduce overprotect overrate overreach overreact overrefine override overrule overrun oversee oversew overshadow overshoot oversimplify oversleep overspecialise overspecialize overspend overspread overstate overstay overstep overstock overstrain overstress overstretch overstuff oversupply overtake overtax overthrow overtire overtop overtrump overturn overuse overvalue overweary overwhelm overwinter overwork overwrite ovulate owe own own up oxidate oxidise oxidize oxygenate oxygenise oxygenize oyster ozonise ozonize Adjective o.k. oafish oaken oaten obdurate obedient obese objectionable objective oblanceolate oblate obligate obligated obligational obligatory obliged obliging oblique oblique-angled obliterable obliterate obliterated oblivious oblong obnoxious obovate obscene obscure obsequious observable observant observational observed observing obsessed obsessional obsessive obsessive-compulsive obsolescent obsolete obstetric obstetrical obstinate obstreperous obstructed obstructive obtainable obtrusive obtuse obviating obvious occasional occidental occipital occluded occlusive occult occupational occupied occurrent oceangoing oceanic ocellated ocher ochre octagonal octal octangular octogenarian octosyllabic octuple ocular odd odd-job odd-pinnate oddish odds-on odious odoriferous odorless odorous odourless oecumenic oecumenical of age of import of sound mind of the essence of unsound mind off off-and-on off-base off-center off-centered off-color off-colour off-guard off-key off-limits off-line off-putting off-site off-street off-the-cuff off-the-peg off-the-rack off-the-shelf off-the-shoulder off-the-wall off-white off guard off her guard off his guard off one's guard off the beaten track off the hook off your guard offbeat offenceless offended offending offenseless offensive offhand offhanded official officious offish offshore offside offsides offstage ohmic oil-bearing oil-fired oil-soluble oiled oily ok okay old old-fashioned old-hat old-line old-maidish old-time old-womanish old-world olde worlde olden older oldish oldline oleaceous oleaginous oleophilic oleophobic olfactive olfactory oligarchic oligarchical olive olive-brown olive-colored olive-coloured olive-drab olive-gray olive-grey olive-like olive-sized olivelike olympian olympic omani ominous omissible omissive omnibus omnidirectional omnifarious omnipotent omnipresent omniscient omnivorous on on-going on-key on-line on-site on-street on-the-job on-the-scene on-the-spot on fire on guard on hand on one's guard on tap on the button on the fence on the go on the hook on the job on the loose on the nose on the offensive on the table on trial on your guard oncologic oncological oncoming one one-armed one-celled one-dimensional one-eared one-eyed one-handed one-horse one-humped one-man one-member one-on-one one-party one-person one-piece one-seed one-seeded one-sided one-time one-to-one one-way one-winged one-woman one-year one-year-old one and only one hundred one hundred eighty one hundred fifteen one hundred fifty one hundred fifty-five one hundred five one hundred forty one hundred forty-five one hundred ninety one hundred one one hundred seventy one hundred seventy-five one hundred sixty one hundred sixty-five one hundred ten one hundred thirty one hundred thirty-five one hundred twenty one hundred twenty-five one thousand oneiric onerous onetime ongoing online only onomastic onomatopoeic onomatopoeical onomatopoetic onshore onside onstage ontogenetic ontological onymous oozing oozy opalescent opaline opaque open open-air open-and-shut open-chain open-collared open-ended open-eyed open-hearth open-minded open-plan open-source opencast opencut opened openhanded openhearted opening openmouthed operable operant operatic operating operational operationalist operative operculate operculated operose ophthalmic opinionated opinionative opisthognathous opponent opportune opportunist opportunistic opposable opposed opposing opposite oppositive oppressed oppressive opprobrious optative opthalmic optic optical optimal optimistic optimum optional opulent oracular oral orange orange-brown orange-colored orange-coloured orange-flowered orange-hued orange-red orange-sized orangish orangish-red oratorical orb-weaving orbicular orbiculate orbital orbitual orchestral orchestrated ordained ordered orderly ordinal ordinary organic organicistic organisational organised organismal organismic organizational organized orgiastic oriental orientated orientating oriented orienting original originative ornamental ornate ornery ornithological oropharyngeal orotund orphaned orphic orthodontic orthodox orthogonal orthographic orthomolecular orthopaedic orthopedic orthopedical orthoptic orthostatic orthotropous orwellian oscan-speaking oscillating oscillatory oscine oscitant osmotic osseous ossicular ossiculate ossiferous ossified osteal ostensible ostensive ostentatious otc other otherwise otherworldly otic otiose ototoxic ottoman out out-and-out out-of-bounds out-of-date out-of-door out-of-pocket out-of-school out-of-the-way out-of-town out of gear out of place out of play out of practice out of print out of reach out of sight out of stock out of the blue out of the question out of true out of use out of whack out of work out or keeping out to outback outboard outbound outbred outcast outcaste outclassed outdated outdoor outdoorsy outer outermost outfitted outflowing outgoing outlandish outlaw outlawed outlined outlying outmoded outmost outraged outrageous outre outrigged outright outside outsize outsized outspoken outspread outstanding outstretched outward outward-bound outward-developing outward-moving oval oval-bodied oval-fruited oval-shaped ovarian ovate oven-ready oven-shaped over over-embellished over-the-counter over-the-hill over-the-top overabundant overactive overage overaged overall overambitious overanxious overarm overawed overbearing overblown overbold overburdened overbusy overcareful overcast overcautious overconfident overcredulous overcritical overcurious overdelicate overdone overdressed overdue overeager overemotional overenthusiastic overexcited overfamiliar overfed overflowing overfond overfull overgenerous overgreedy overgrown overhand overhanded overhasty overhead overheated overindulgent overjealous overjoyed overladen overland overlarge overloaded overlooked overlooking overlying overmodest overmuch overnice overnight overpowering overpriced overprotective overproud overreaching overrefined overriding overripe oversea overseas oversensitive overserious oversewn oversexed overshot oversize oversized oversolicitous overstated overstrung overstuffed oversubscribed oversuspicious overt overturned overvaliant overweening overweight overwhelming overwrought overzealous oviform ovine oviparous ovoid ovoviviparous ovular owing owlish own owned owner-occupied ownerless ox-eyed oxford-gray oxford-grey oxidative oxidised oxidizable oxidized oxonian Adverb o'clock o'er o.k. obdurately obediently objectionably objectively obligatorily obligingly obliquely obnoxiously obscenely obscurely obsequiously observably observantly observingly obsessionally obsessively obstinately obstreperously obstructively obtrusively obtusely obviously occasionally oddly odiously of a sudden of all time of course of each person of late of necessity off off-hand off-the-clock off and on off the cuff off the record offensively offhand offhanded offhandedly officially officiously offshore offside offstage oft often oftener oftentimes ofttimes ok okay ominously on on a higher floor on a lower floor on a regular basis on air on all fours on an individual basis on an irregular basis on and off on approval on average on base on board on camera on earth on faith on it on occasion on one hand on paper on purpose on request on that on that point on the average on the button on the coattails on the contrary on the dot on the face of it on the fly on the nose on the one hand on the other hand on the q.t. on the qt on the side on the sly on the spot on the spur of the moment on the way on the whole on the wing on time once once again once and for all once in a while once more one-on-one one-sidedly one after another one at a time one by one one one's coattails one time onerously only only if only too only when onshore onstage onward onwards opaquely openly operationally operatively opportunely opposite oppositely oppressively optically optimally optimistically optionally opulently or else or so orad orally ordinarily organically organizationally originally ornamentally ornately osmotically ostensibly ostentatiously other than otherwise out out and away out front out loud out of out of doors out of hand out of nothing out of place out of sight out of the blue out of the way out of thin air out of view out of wedlock outdoors outlandishly outrageously outright outside outside marriage outspokenly outstandingly outward outwardly outwards over over again over and over over and over again over here overbearingly overboard overhead overleaf overly overmuch overnight overpoweringly oversea overseas overside overtime overtly overwhelmingly owlishly Noun o o'brien o'casey o'connor o'flaherty o'hara o'keeffe o'neill o'toole o. henry o.e.d. o.k. o level o ring oaf oahu oahu island oak oak-leaved goosefoot oak apple oak blight oak chestnut oak fern oak leaf cluster oak tree oakland oakleaf goosefoot oakley oakum oar oarfish oarlock oarsman oarsmanship oarswoman oas oasis oast oast house oat oat cell carcinoma oatcake oates oath oatmeal oatmeal cookie oaxaca oaxaca de juarez ob ob river obadiah obbligato obduracy obeah obeche obechi obedience obedience plant obedient plant obeisance obelion obelisk oberson obesity obesity diet obfuscation obi obidoxime chloride obiism obit obiter dictum obituary object object-oriented database object-oriented database management system object-oriented programing object-oriented programing language object-oriented programming object-oriented programming language object ball object code object glass object language object lens object lesson object of a preposition object of the verb object program object recognition objectification objection objectionableness objective objective case objective lens objectiveness objectivity objector objet d'art objurgation oblanceolate leaf oblate oblateness oblation obligate anaerobe obligation obligato obliger obligingness oblique oblique angle oblique bandage oblique case oblique triangle oblique vein of the left atrium obliqueness obliquity obliteration obliterator oblivion obliviousness oblong oblong leaf oblong woodsia oblongness obloquy obnoxiousness oboe oboe d'amore oboe da caccia oboist obolus obovate leaf obscenity obscurantism obscurantist obscureness obscurity obsequiousness observance observation observation dome observation post observation station observation tower observatory observed fire observer observer's meridian obsession obsessive obsessive-compulsive obsessive-compulsive disorder obsessive-compulsive personality obsessiveness obsessivity obsidian obsolescence obsoleteness obstacle obstacle race obstetrical delivery obstetrical toad obstetrician obstetrics obstinacy obstinance obstipation obstreperousness obstructer obstruction obstruction of justice obstructionism obstructionist obstructive shock obstructor obstruent obtainment obtention obtrusiveness obturator obturator vein obtuse-angled triangle obtuse angle obtuse leaf obtuse triangle obtuseness obverse obviation obviousness oca ocarina occam occam's razor occasion occasions occident occidental occidentalism occipital bone occipital cortex occipital gyrus occipital lobe occipital protuberance occipital vein occipitomastoid suture occiput occitan occluded front occlusion occlusive occult occult arts occultation occultism occultist occupancy occupancy rate occupant occupation occupation licence occupation license occupational disease occupational group occupational hazard occupational safety and health act occupational safety and health administration occupational therapy occupier occurrence occurrent ocean ocean bottom ocean current ocean floor ocean liner ocean perch ocean pout ocean state ocean sunfish ocean trip oceanaut oceanfront oceania oceanic oceanic abyss oceanic bird oceanic bonito oceanic whitetip shark oceanica oceanid oceanites oceanites oceanicus oceanographer oceanography oceanology oceanus ocellated turkey ocellus ocelot ocher ochlocracy ochna ochna family ochna serrulata ochnaceae ochoa ochotona ochotona collaris ochotona princeps ochotonidae ochre ochroma ochroma lagopus ochronosis ochs ocimum ocimum basilicum ockham ockham's razor oconee bells ocotillo oct octad octadecanoic acid octagon octahedron octal digit octal notation octal number system octal numeration system octameter octane octane number octane rating octanedioic acid octans octant octave octavian octavo octet octette octillion october october 12 october 24 october revolution octoberfest octogenarian octonary octopod octopoda octopodidae octopus octoroon octosyllable octroi ocular ocular muscle oculism oculist oculomotor oculomotor nerve oculopharyngeal muscular dystrophy oculus oculus dexter oculus sinister ocyurus ocyurus chrysurus od odalisque odd-even check odd-job man odd-leg caliper odd-pinnate leaf odd-toed ungulate odd fellow odd fish odd hassel odd man out oddball oddity oddment oddments oddness oddone colonna odds odds-maker odds and ends ode oder oder river odesa odessa odets odin odiousness odist odium odo odo of lagery odoacer odobenidae odobenus odobenus divergens odobenus rosmarus odocoileus odocoileus hemionus odocoileus hemionus columbianus odocoileus virginianus odometer odonata odonate odontalgia odontaspididae odontaspis odontaspis taurus odontiasis odontoceti odontoglossum odontoid process odontology odontophorus odor odour odovacar odovakar odynophagia odysseus odyssey oecanthus oecanthus fultoni oecumenism oed oedema oedipal complex oedipus oedipus complex oedipus rex oedogoniaceae oedogoniales oedogonium oeil de boeuf oenanthe oenanthe aquatica oenanthe crocata oengus oenologist oenology oenomel oenophile oenothera oenothera biennis oenothera fruticosa oenothera macrocarpa oersted oesophageal reflux oesophageal veins oesophagitis oesophagogastric junction oesophagoscope oesophagus oesterreich oestradiol oestridae oestriol oestrogen oestrone oestrus oestrus ovis oeuvre off-axis reflector off-broadway off-day off-licence off-line equipment off-line operation off-roader off-season off-speed pitch off-white off year offal offbeat offenbach offence offender offense offensive offensive activity offensiveness offer offer price offerer offering offeror offertory office office-bearer office block office boy office building office furniture office of inspector general office of intelligence support office of management and budget office of naval intelligence office of the dead office staff officeholder officer officer's mess official official document official emissary official immunity officialdom officialese officiant officiating officiation officiousness offing offprint offset offset lithography offset printing offsetting balance offshoot offshore rig offside offspring offstage ofo oftenness ogalala ogcocephalidae ogden ogden nash ogdoad ogee ogee arch ogive oglala ogler ogre ogress oh ohio ohio buckeye ohio goldenrod ohio river ohio state university ohioan ohm ohm's law ohmage ohmic resistance ohmmeter oig oil oil-hardened steel oil-industry analyst oil-rich seed oil-water interface oil beetle oil burner oil business oil cake oil cartel oil change oil color oil colour oil company oil conservation oil filter oil furnace oil future oil geologist oil gland oil heater oil industry oil lamp oil meal oil nut oil of cloves oil of turpentine oil of vitriol oil of wintergreen oil paint oil painter oil painting oil palm oil pipeline oil pressure oil production oil pump oil refinery oil rig oil rigger oil shale oil slick oil stain oil tanker oil tycoon oil well oilbird oilcan oilcloth oiler oilfield oilfish oiliness oilman oilpaper oilrig oilseed oilskin oilstone oilstove oink ointment oireachtas ois ojibwa ojibway ojos del salado ok oka okapi okapia okapia johnstoni okay okeechobee okeechobee waterway okefenokee swamp okeh oken okenfuss okey okinawa okinawa campaign oklahoma oklahoma city oklahoman okra okra plant oktoberfest ola olaf ii olav ii old old-age insurance old-age pension old-age pensioner old-fashionedness old-field toadflax old-maid's bonnet old-man-of-the-woods old-timer old age old bag old bailey old boy old boy network old bulgarian old bullion old catholic old catholic church old church slavic old church slavonic old codger old colony old country old delhi old dominion old dominion state old english old english sheepdog old faithful old fashioned old french old frisian old geezer old glory old gold old growth old guard old hand old hickory old high german old icelandic old irish old ironsides old italian old lady old latin old line state old maid old maid flower old man old man's beard old man of the mountain old master old money old nick old norse old north french old north state old person old prussian old rose old salt old saxon old school old school tie old sledge old south old squaw old stager old style old style calendar old style font old testament old times old witch grass old witchgrass old wives' tale old woman old world old world beaver old world buffalo old world chat old world coot old world coral snake old world crayfish old world flycatcher old world hop hornbeam old world jay old world least weasel old world leishmaniasis old world mistletoe old world monkey old world oriole old world porcupine old world quail old world rabbit old world robin old world scops owl old world vulture old world warbler old world white pelican old world yew oldenburg oldfield oldie oldness oldster oldtimer olduvai gorge oldwench oldwife olea olea cunninghamii olea europaea olea lanceolata oleaceae oleaginousness oleales oleander oleander fern oleandra oleandra mollis oleandra neriiformis oleandraceae olearia olearia argophylla olearia haastii oleaster oleaster family olecranon olecranon process oled olefin olefine oleic acid olein oleo oleo oil oleomargarine oleoresin oleoresin capiscum olfaction olfactory brain olfactory bulb olfactory impairment olfactory modality olfactory nerve olfactory organ olfactory perception olfactory property olfactory sensation olfersia olfersia cervina olga korbut olibanum oligarch oligarchy oligocene oligocene epoch oligochaeta oligochaete oligochaete worm oligoclase oligodactyly oligodendria oligodendrocyte oligodendroglia oligodontia oligomenorrhea oligoplites oligopoly oligoporus oligoporus leucospongia oligosaccharide oligospermia oliguria olimbos olive olive-drab uniform olive-green olive-tree agaric olive branch olive brown olive drab olive family olive green olive oil olive ridley olive tree olivenite oliver oliver cromwell oliver ellsworth oliver goldsmith oliver hardy oliver hazard perry oliver heaviside oliver stone oliver wendell holmes oliver wendell holmes jr. olivier olivine olla olla podrida ollari olm olmec olmsted ology olympia olympiad olympian olympian games olympian zeus olympic games olympic god olympic national park olympic salamander olympics olympus omaha oman omani omani monetary unit omani rial omar bradley omar khayyam omar nelson bradley omasum omayyad omb ombu ombudsman omdurman omega omega-3 omega-3 fatty acid omega-6 omega-6 fatty acid omega centauri omelet omelet pan omelette omelette pan omen omental bursa omentum omeprazole omerta omicron omission omiya ommastrephes ommatidium ommiad omnibus omnidirectional antenna omnidirectional radio range omnidirectional range omnipotence omnipresence omnirange omniscience omnium-gatherum omnivore omomyid omomyid group omophagia omotic omphalocele omphalos omphaloskepsis omphalotus omphalotus illudens omphalus omsk on-license on-line database on-off switch on/off switch on the qui vive on the road on tour onager onagraceae onanism onanist once-over onchocerciasis oncidium oncidium papilio oncidium papilio kramerianum oncogene oncologist oncology oncoming oncorhynchus oncorhynchus keta oncorhynchus kisutch oncorhynchus nerka oncorhynchus tshawytscha oncovin ondaatje ondatra ondatra zibethica one one-and-one one-armed bandit one-billionth one-dimensional language one-dimensionality one-eighth one-fifth one-flowered pyrola one-flowered wintergreen one-fourth one-half one-hitter one-hundred-millionth one-hundred-thousandth one-hundredth one-liner one-man rule one-millionth one-night stand one-ninth one-off one-quadrillionth one-quarter one-quintillionth one-seventh one-sixteenth one-sixth one-sixtieth one-sixty-fourth one-spot one-step one-ten-thousandth one-tenth one-third one-thirty-second one-thousandth one-trillionth one-twelfth one-upmanship one-way light time one-way street one c one dollar bill one iron one million million one million million million one of the boys one percent one shot one thousand one thousand million one thousand thousand onega oneida oneirism oneiromancer oneiromancy oneness onerousness oni onion onion bagel onion bread onion butter onion dome onion louse onion mildew onion plant onion roll onion salt onion smut onion stem onion thrips onion yellow-dwarf virus onion yellow dwarf onionskin oniscidae oniscus onlooker ono onobrychis onobrychis viciaefolia onobrychis viciifolia onoclea onoclea sensibilis onoclea struthiopteris onomancer onomancy onomasticon onomastics onomatomania onomatopoeia onondaga ononis ononis repens ononis spinosa onopordon onopordon acanthium onopordum onopordum acanthium onosmodium onrush onsager onset onslaught ontario ontogenesis ontogeny ontology onus onward motion onychium onychogalea onycholysis onychomys onychophora onychophoran onychosis onyx onyx marble onyxis oocyte oodles oogenesis oology oolong oom paul kruger oomph oomycetes oophorectomy oophoritis oophorosalpingectomy oort oort cloud oosphere oospore ootid ooze ooze leather oozing op art opacification opacity opah opal opal glass opalescence opaque gem opaqueness opcw opec opel open open-air market open-air marketplace open-angle glaucoma open-class word open-door policy open-end credit open-end fund open-end investment company open-end wrench open-face sandwich open-heart surgery open-hearth furnace open-hearth process open account open air open chain open circuit open door open fireplace open fracture open frame open house open interval open letter open marriage open order open primary open sandwich open secret open sesame open shop open sight open society open university open weave openbill opencast mining opener openhandedness opening opening line opening move opening night openness openside plane openwork opepe opera opera bouffe opera cloak opera comique opera company opera glasses opera hat opera hood opera house opera star operagoer operand operant conditioning operatic star operating budget operating capability operating capital operating cost operating expense operating instructions operating microscope operating procedure operating room operating statement operating surgeon operating system operating table operating theater operating theatre operation operation code operation desert storm operational casualty operational cell operational damage operationalism operations operations research operative operative field operator operator gene operculum operetta operon operoseness opheodrys opheodrys aestivus opheodrys vernalis ophidia ophidian ophidiidae ophidism ophiodon ophiodon elongatus ophiodontidae ophioglossaceae ophioglossales ophioglossum ophioglossum pendulum ophiolatry ophiophagus ophiophagus hannah ophisaurus ophiuchus ophiurida ophiuroidea ophryon ophrys ophrys apifera ophrys insectifera ophrys muscifera ophrys sphegodes ophthalmectomy ophthalmia ophthalmia neonatorum ophthalmic artery ophthalmic vein ophthalmitis ophthalmologist ophthalmology ophthalmoplegia ophthalmoscope ophthalmoscopy opiate opiliones opinion opinion poll opisthobranchia opisthocomidae opisthocomus opisthocomus hoazin opisthognathidae opisthorchiasis opisthotonos opium opium addict opium den opium poppy opium taker opopanax oporto opossum opossum rat opossum shrimp opossum wood oppenheimer opponent opportuneness opportunism opportunist opportunistic infection opportunity opportunity cost opposer opposite opposite number opposite word oppositeness opposition oppression oppressiveness oppressor opprobrium ops opsanus tau opsin opsonin opsonisation opsonization optative optative mood optez optic optic axis optic chiasm optic chiasma optic cup optic disc optic disk optic nerve optic radiation optic tract optical aberration optical bench optical condenser optical crown optical crown glass optical density optical device optical disc optical disk optical fiber optical fibre optical flint optical fusion optical glass optical illusion optical instrument optical lens optical maser optical opacity optical phenomenon optical prism optical pyrometer optical telescope optician optics optimisation optimism optimist optimization optimum option optometrist optometry opulence opuntia opuntia cholla opuntia lindheimeri opuntia tuna opuntiales opus opv or or circuit or gate orach orache oracle oracle of apollo oracle of delphi oradexon oral oral cancer oral cavity oral communication oral contraception oral contraceptive oral contraceptive pill oral contract oral exam oral examination oral fissure oral herpes oral personality oral phase oral poliovirus vaccine oral presentation oral roberts oral sex oral smear oral stage oran orang orange orange-blossom orchid orange-juice concentrate orange balsam orange bat orange daisy orange fleabane orange free state orange grass orange group orange grove orange hawkweed orange horseshoe bat orange juice orange liqueur orange marmalade orange milkweed orange milkwort orange mushroom pimple orange order orange peel orange peel fungus orange pekoe orange red orange rind orange river orange sneezeweed orange soda orange toast orange tortrix orange tree orange yellow orange zest orangeade orangeman orangeness orangery orangewood orangutan orangutang orasone oration orator oratorio oratory orb orb-weaver orb-weaving spider orb web orbiculate leaf orbignya orbignya cohune orbignya martiana orbignya phalerata orbignya spesiosa orbison orbit orbit period orbital cavity orbital motion orbital plane orbital point orbital rotation orbitale orbiter orca orchard orchard apple tree orchard grass orchard oriole orchestia orchestiidae orchestra orchestra pit orchestral bells orchestration orchestrator orchid orchid cactus orchid family orchid tree orchidaceae orchidaceous plant orchidales orchidalgia orchidectomy orchiectomy orchil orchiopexy orchis orchis mascula orchis papilionaceae orchis spectabilis orchitis orchotomy orcinus orcinus orca orcus orczy ord kangaroo rat ordainer ordeal ordeal bean ordeal tree order order-chenopodiales order acarina order accipitriformes order actinaria order actiniaria order actinomycetales order actinomyxidia order aepyorniformes order agaricales order alcyonaria order alismales order amoebida order amoebina order amphipoda order anacanthini order anaspida order andreaeales order anguilliformes order anoplura order anostraca order anseriformes order anthocerotales order anura order aphyllophorales order aplacophora order apodes order apodiformes order apterygiformes order arales order araneae order araneida order aristolochiales order arms order artiodactyla order aspergillales order auriculariales order batoidei order batrachia order belemnoidea order bennettitales order berycomorphi order blastocladiales order book order branchiura order bryales order campanulales order caprimulgiformes order carnivora order caryophyllales order casuariiformes order casuarinales order caudata order cestida order cetacea order charadriiformes order charales order chelonethida order chelonia order chiroptera order chlorococcales order chytridiales order ciconiiformes order cilioflagellata order coccidia order code order coleoptera order collembola order columbiformes order colymbiformes order commelinales order coniferales order conodonta order conodontophorida order coraciiformes order cordaitales order corrodentia order crocodilia order crocodylia order cuculiformes order cycadales order cycadofilicales order cyclostomata order cydippea order cydippida order cydippidea order cypriniformes order decapoda order dermaptera order dermoptera order diapensiales order dicranales order dictyoptera order dinocerata order dinoflagellata order dinornithiformes order diptera order discocephali order ebenales order edentata order embiodea order embioptera order endomycetales order entomophthorales order ephemerida order ephemeroptera order equisetales order ericales order erysiphales order eubacteriales order eubryales order euphausiacea order eurotiales order eurypterida order exocycloida order fagales order falconiformes order filicales order foraminifera order form order fucales order gadiformes order galliformes order ganoidei order gaviiformes order gentianales order geophilomorpha order geraniales order ginkgoales order gnetales order graminales order gregarinida order gruiformes order guttiferales order gymnophiona order haemosporidia order haplosporidia order heliozoa order helotiales order hemiptera order heterosomata order heterotrichales order hymenogastrales order hymenoptera order hypericales order hypermastigina order hypocreales order hyracoidea order ichthyosauria order ictodosauria order insectivora order insessores order isoetales order isopoda order isoptera order isospondyli order juglandales order jungermanniales order lagomorpha order laminariales order lechanorales order lepidodendrales order lepidoptera order lichenales order liliales order lobata order loricata order lycoperdales order lycopodiales order lyginopteridales order madreporaria order mallophaga order malvales order mantophasmatodea order marattiales order marchantiales order marsupialia order mecoptera order moniliales order monotremata order mucorales order musales order myaceae order mycelia sterilia order mycoplasmatales order mycrosporidia order myricales order myrtales order mysidacea order myxobacterales order myxobacteria order myxobacteriales order myxosporidia order naiadales order neuroptera order nidulariales order notostraca order nudibranchia order octopoda order odonata order oedogoniales order of business order of magnitude order of our lady of mount carmel order of payment order of saint benedict order of the day order of the purple heart order oleales order ophioglossales order opiliones order opuntiales order orchidales order ornithischia order orthoptera order ostariophysi order osteoglossiformes order ostracodermi order palmales order pandanales order papaverales order paper order parietales order passeriformes order pectinibranchia order pediculati order pedipalpi order pelecaniformes order pelycosauria order perciformes order percomorphi order perissodactyla order peronosporales order pezizales order phalangida order phallales order phasmatodea order phasmida order pholidota order picariae order piciformes order piperales order plantaginales order platyctenea order plecoptera order plectognathi order pleuronectiformes order plumbaginales order podicipediformes order podicipitiformes order polemoniales order polygonales order polymastigina order polypodiales order primates order primulales order proboscidea order procellariiformes order proteales order protura order pseudomonadales order pseudoscorpiones order pseudoscorpionida order psilophytales order psilotales order psittaciformes order psocoptera order pterosauria order pulmonata order pycnogonida order radiolaria order rajiformes order ranales order ranunculales order raptores order rhamnales order rheiformes order rhoeadales order rhynchocephalia order rickettsiales order rodentia order rosales order rubiales order salicales order salientia order santalales order sapindales order saprolegniales order sarcosporidia order sarraceniales order saurischia order sauropterygia order scandentia order sclerodermatales order scleroparei order scorpionida order scrophulariales order secotiales order selaginellales order siluriformes order siphonaptera order siphonophora order sirenia order solenichthyes order solenogastres order spatangoida order sphaeriales order sphaerocarpales order sphagnales order sphenisciformes order spirochaetales order squamata order stegocephalia order stereospondyli order stomatopoda order strigiformes order struthioniformes order synentognathi order taxales order temnospondyli order testacea order testudinata order testudines order tetraodontiformes order thecodontia order therapsida order thymelaeales order thysanoptera order thysanura order tinamiformes order torpediniformes order tremellales order trichoptera order trogoniformes order tuberales order tubulidentata order tulostomatales order ulvales order umbellales order uredinales order urodella order uropygi order urticales order ustilaginales order volvocales order xiphosura order xyridales order zeomorphi order zygnemales order zygnematales ordered series orderer ordering orderliness orderly orderly sergeant ordinal ordinal number ordinance ordinand ordinariness ordinary ordinary annuity ordinary bicycle ordinary care ordinary life insurance ordinary shares ordinate ordination ordnance ordnance store ordnance survey ordovician ordovician period ordure ore ore bed ore dressing ore processing oread oreamnos oreamnos americanus orectolobidae orectolobus orectolobus barbatus oregano oregon oregon alder oregon ash oregon cedar oregon crab apple oregon fir oregon grape oregon holly grape oregon jargon oregon larch oregon lily oregon maple oregon myrtle oregon oak oregon pine oregon white oak oregonian oreide oreo oreo cookie oreopteris oreopteris limbosperma oreortyx oreortyx picta palmeri orestes orff organ organ-grinder organ donor organ loft organ of corti organ of hearing organ of speech organ pipe organ stop organ transplant organdie organdy organelle organic organic brain syndrome organic chemistry organic compound organic disorder organic evolution organic fertiliser organic fertilizer organic law organic light-emitting diode organic phenomenon organic process organic structure organicism organification organisation organiser organism organist organization organization chart organization expense organization for the prohibition of chemical weapons organization man organization of american states organization of petroleum-exporting countries organization of the oppressed on earth organized crime organized labor organized religion organizer organon organophosphate organophosphate nerve agent organs organza orgasm orgy oriel oriel window orient oriental oriental alabaster oriental arborvitae oriental beetle oriental bittersweet oriental black mushroom oriental bush cherry oriental cherry oriental cockroach oriental garlic oriental person oriental plane oriental poppy oriental roach oriental scops owl oriental sore oriental spruce oriental studies orientalism orientalist orientation orientation course orifice oriflamme origami origanum origanum dictamnus origanum majorana origanum vulgare origen origin original original sin originalism originality origination origination fee originator orinasal orinasal phone orinase orinoco orinoco river oriole oriolidae oriolus oriolus oriolus orion orison orissa orites orites excelsa oriya orizaba orkney islands orlando orlando di lasso orleanais orleanism orleanist orleans orlon orlop orlop deck orly orly group ormandy ormazd ormer ormolu ormosia ormosia coarctata ormosia monosperma ormuzd ornament ornamental ornamentalism ornamentalist ornamentation ornateness orneriness ornithine ornithischia ornithischian ornithischian dinosaur ornithogalum ornithogalum pyrenaicum ornithogalum thyrsoides ornithogalum umbellatum ornithologist ornithology ornithomimid ornithomimida ornithopod ornithopod dinosaur ornithopoda ornithopter ornithorhynchidae ornithorhynchus ornithorhynchus anatinus ornithosis orobanchaceae orogeny orography oroide orology orono orontium orontium aquaticum oropharynx orozco orphan orphan site orphanage orphanhood orphans' asylum orphenadrine orpheus orphrey orpiment orpin orpine orpington orr orrery orris orrisroot orson welles ortalis ortega ortega y gasset orthicon orthilia orthoboric acid orthochorea orthochromatic film orthoclase orthodontia orthodontic braces orthodontic treatment orthodontics orthodontist orthodonture orthodox catholic church orthodox church orthodox jew orthodox judaism orthodox sleep orthodoxy orthoepist orthoepy orthogonal opposition orthogonality orthography orthomorphic projection orthomyxovirus orthopaedics orthopaedist orthopedics orthopedist orthophosphate orthophosphoric acid orthophosphorous acid orthopnea orthopristis orthopristis chrysopterus orthopter orthoptera orthopteran orthopteron orthopterous insect orthoptics orthoptist orthoscope orthostatic hypotension orthotomus orthotomus sutorius orthotropous ovule ortilis vetula macalli ortolan ortolan bunting ortygan orudis orudis kt orumiyeh oruvail orville wright orwell orycteropodidae orycteropus orycteropus afer oryctolagus oryctolagus cuniculus oryx oryx gazella oryza oryza sativa oryzomys oryzomys palustris oryzopsis oryzopsis hymenoides oryzopsis miliacea orzo os os breve os capitatum os frontale os hamatum os hyoideum os ischii os longum os lunatum os nasale os palatinum os pisiforme os pubis os scaphoideum os sesamoideum os sphenoidale os tarsi fibulare os temporale os trapezium os trapezoideum os triquetrum os zygomaticum osage osage orange osage river osaka osaka bay osama bin laden osasco osborne oscan oscar oscar fingal o'flahertie wills wilde oscar hammerstein oscar hammerstein ii oscar palmer robertson oscar robertson oscar wilde oscheocele oscheocoele oscillation oscillator oscillatoriaceae oscillogram oscillograph oscilloscope oscine oscine bird oscines oscitance oscitancy osco-umbrian osculating circle osculation osculator osha osier osip emilevich mandelstam osip mandelstam osiris oslo osman i osmanli osmanthus osmanthus americanus osmeridae osmerus osmerus eperlanus osmerus mordax osmiridium osmitrol osmium osmoreceptor osmosis osmotic pressure osmund osmunda cinnamonea osmunda clatonia osmunda regalis osmundaceae osprey osseous labyrinth osseous tissue ossete ossicle ossiculum ossification osso buco ossuary ostariophysi osteichthyes osteitis osteitis deformans ostensive definition ostensorium ostentation ostentatiousness osteoarthritis osteoblast osteoblastoma osteochondroma osteoclasis osteoclast osteocyte osteodystrophy osteogenesis imperfecta osteogenic sarcoma osteoglossidae osteoglossiformes osteologer osteologist osteology osteolysis osteoma osteomalacia osteomyelitis osteopath osteopathist osteopathy osteopetrosis osteophyte osteoporosis osteosarcoma osteosclerosis osteosclerosis congenita osteostracan osteostraci osteotomy ostiarius ostiary ostinato ostiole ostler ostomy ostraciidae ostracism ostracod ostracoda ostracoderm ostracodermi ostrava ostrea ostrea gigas ostreidae ostrich ostrich fern ostrogoth ostrya ostrya carpinifolia ostrya virginiana ostryopsis ostwald ostwald's theory of indicators ostyak ostyak-samoyed oswald oswald spengler oswald veblen oswego tea otaheite arrowroot otaheite arrowroot starch otalgia otaria otaria byronia otariidae otc market otc security otc stock othello otherness otherworld otherworldliness othman i otho otho i otho of lagery othonna otic ganglion otides otididae otis otis skinner otis tarda otitis otitis externa otitis interna otitis media oto otoe otoganglion otolaryngologist otolaryngology otologist otology otoplasty otorhinolaryngologist otorhinolaryngology otorrhea otosclerosis otoscope ottar ottava rima ottawa ottawa river otter otter hound otter shrew otterhound ottmar mergenthaler otto frisch otto fritz meyerhof otto hahn otto heinrich warburg otto i otto jespersen otto loewi otto meyerhof otto neumann sverdrup otto robert frisch otto the great otto von bismarck otto wagner ottoman ottoman dynasty ottoman empire ottoman turk ottorino respighi ottumwa otus otus asio otus scops otus sunia ouachita ouachita river oubliette ouguiya ouija ouija board oujda ounce our lady's bedstraw our lady's mild thistle our lord's candle ouranopithecus ouranos ouse ouse river ousel ouster ousting out out-and-outer out-basket out-migration out-of-body experience out-of-court settlement out-of-doors out-of-the-box thinking out-tray out of bounds outage outaouais outback outboard outboard motor outboard motorboat outbreak outbuilding outburst outcast outcaste outcome outcrop outcropping outcry outdoor game outdoor man outdoor sport outdoor stage outdoors outdoorsman outdoorswoman outer boundary outer ear outer garment outer hebrides outer mongolia outer planet outer space outercourse outerwear outfall outfield outfielder outfit outfitter outfitting outflow outgo outgoer outgrowth outhouse outing outlander outlandishness outlaw outlawry outlay outlet outlet box outlier outline outlook outpatient outport outpost outpouring output output-to-input ratio output contract output device output file output program output routine output signal outrage outrageousness outreach outrider outrigger outrigger canoe outset outside outside caliper outside clinch outside door outside loop outside mirror outsider outsider art outsize outskirt outskirts outsole outspokenness outstation outstroke outtake outthrust outturn outwardness outwork ouzel ouzo ov oval oval kumquat oval office oval window ovalbumin ovalipes ovalipes ocellatus ovarian artery ovarian cyst ovarian pregnancy ovarian vein ovariectomy ovaritis ovary ovate leaf ovation oven oven stuffer oven stuffer roaster oven thermometer ovenbird ovenware over over-crowding over-the-counter drug over-the-counter market over-the-counter medicine over-the-shoulder bombing over the counter security over the counter stock overabundance overachievement overachiever overacting overactivity overage overall overanxiety overappraisal overbearingness overbid overbite overburden overcall overcapitalisation overcapitalization overcast overcasting overcharge overclothes overcoat overcoating overcomer overcompensation overconfidence overcredulity overcrossing overcup oak overdraft overdraft credit overdrive overeating overemphasis overestimate overestimation overexertion overexploitation overexposure overfeeding overflight overflow overflow incontinence overgarment overgrowth overhand knot overhand pitch overhand stitch overhang overhaul overhead overhead projector overhead railway overheating overindulgence overkill overlap overlapping overlay overlayer overlip overload overlook overlord overlordship overmantel overmuch overmuchness overnight bag overnight case overnighter overpass overpayment overplus overpopulation overpressure overprint overproduction overprotection overrating overreaction overreckoning overrefinement override overrun overseas cap overseas telegram overseer oversensitiveness overshielding overshoe overshoot oversight oversimplification overskirt overspill overstatement overstrain overstuffed chair oversupply overt operation overtaking overthrow overthrust fault overtime overtime period overtolerance overtone overture overturn overuse overutilisation overutilization overvaluation overview overweight overwork overworking ovibos ovibos moschatus ovid oviduct oviedo ovimbundu ovipositor oviraptorid ovis ovis ammon ovis aries ovis canadensis ovis montana dalli ovis musimon ovis poli ovis vignei ovocon ovoflavin ovoid ovolo ovotestis ovral ovrette ovulation ovulation method ovulation method of family planning ovule ovulen ovum owen owen glendower owen wister owens owensboro owl owlclaws owlet owlet moth owlt own goal own right owner owner-driver owner-occupier ownership ox ox-eyed daisy oxacillin oxalacetate oxalacetic acid oxalate oxalic acid oxalidaceae oxalis oxalis acetosella oxalis caprina oxalis cernua oxalis corniculata oxalis crenata oxalis pes-caprae oxalis tuberosa oxalis violacea oxaloacetate oxaloacetic acid oxandra oxandra lanceolata oxaprozin oxazepam oxblood red oxbow oxbow lake oxbridge oxcart oxen oxeye oxeye daisy oxford oxford english oxford english dictionary oxford gray oxford grey oxford movement oxford university oxheart oxheart cherry oxidant oxidase oxidation oxidation-reduction oxidation-reduction indicator oxidation number oxidation state oxidative phosphorylation oxide oxidisation oxidiser oxidization oxidized ldl cholesterol oxidizer oxidizing agent oxidoreductase oxidoreduction oxime oximeter oxlip oxonian oxtail oxtail soup oxtant oxtongue oxyacetylene oxyacetylene torch oxyacid oxybelis oxybenzene oxybutyric acid oxycephaly oxydendrum oxydendrum arboreum oxygen oxygen acid oxygen debt oxygen deficit oxygen mask oxygenase oxygenation oxyhaemoglobin oxyhemoglobin oxylebius oxylebius pictus oxymoron oxyopia oxyphenbutazone oxyphencyclimine oxytetracycline oxytetracycline hydrochloride oxytocic oxytocic drug oxytocin oxytone oxytropis oxytropis lambertii oxyura oxyura jamaicensis oxyuranus oxyuranus scutellatus oxyuridae oyabun oyster oyster-fish oyster agaric oyster bank oyster bar oyster bed oyster catcher oyster crab oyster cracker oyster dressing oyster fish oyster fungus oyster mushroom oyster park oyster plant oyster shell oyster stew oyster stuffing oystercatcher oysterfish oysters rockefeller oz. ozaena ozark chinkapin ozark chinquapin ozark mountains ozark plateau ozark sundrops ozarks ozawa ozena ozocerite ozokerite ozone ozone hole ozone layer ozone sickness ozonide ozonium ozonosphere ozothamnus ozothamnus secundiflorus Related Content Daily Word Quiz: plausible Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language