/ Dictionary / Index M mgd: Meaning and Definition of Find definitions for: mgd Pronunciation: [key] millions of gallons per day. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. MGB MGk. Related Content Daily Word Quiz: belligerent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language