/ Dictionary / Index M mm Hg: Meaning and Definition of Find definitions for: mm Hg Pronunciation: [key] millimeter of mercury. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. M.Mgt.E. mmho Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language