/ Dictionary / Index T twenty-first: Meaning and Definition of Find definitions for: twen•ty-first Pronunciation: (twen'tē-fûrst', twun'-), [key] — adj. next after the twentieth; being the ordinal number for 21. being one of 21 equal parts. —n. a twenty-first part, esp. of one (). the twenty-first member of a series. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: twenty-first (Thesaurus) Twenty-fifth Amendment Twenty-first Amendment Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language