/ Dictionary / Index M menadione: Meaning and Definition of Find definitions for: men•a•di•one Pronunciation: (men"u-dī'ōn), [key] — n. Pharm. a synthetic yellow crystalline powder, CHO, insoluble in water, used as a vitamin K supplement. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: menadione (Thesaurus) menad Menado Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language