/ Dictionary / Index F fifty-one: Meaning and Definition of Find definitions for: fif•ty-one Pronunciation: (fif'tē-wun'), [key] — n. a cardinal number, 50 plus 1. a symbol for this number, as 51 or LI. a set of this many persons or things. —adj. amounting to 51 in number. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: fifty-one (Thesaurus) fifty-ninth fiftypenny Related Content Daily Word Quiz: reluctant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language