/ Dictionary / Index M mountainous: Meaning and Definition of Find definitions for: moun•tain•ous Pronunciation: (moun'tn-us), [key] — adj. abounding in mountains: a mountainous wilderness. of the nature of a mountain. resembling a mountain or mountains, as being very large and high: mountainous waves. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mountainous (Thesaurus) mountain mint mountain oyster Related Content Daily Word Quiz: candid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language