/ Dictionary / Index M momentous: Meaning and Definition of Find definitions for: mo•men•tous Pronunciation: (mō-men'tus), [key] — adj. of great or far-reaching importance or consequence: a momentous day. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: momentous (Thesaurus) moment of truth momentum Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language