/ Dictionary / Index M mu: Meaning and Definition of Find definitions for: mu Pronunciation: (my, m), [key] — n. the 12th letter of the Greek alphabet (M, &mgr;). the consonant sound represented by this letter. micron (def. 1). Mu Pronunciation: (my, m), [key] — n. a legendary lost continent supposed to have sunk into the SW Pacific Ocean at about the same time that Atlantis disappeared into the Atlantic Ocean. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mu (Thesaurus) Mtwara Mubarak Related Content Daily Word Quiz: placid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language