/ Dictionary / Index M moo: Meaning and Definition of Find definitions for: moo Pronunciation: (m), [key] — v., n., pl. mooed, moo•ing, moos. —v.i. to utter the characteristic deep sound of a cow; low. —n. a mooing sound. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: moo (Thesaurus) monzonite mooch Related Content Daily Word Quiz: penury Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language