/ Dictionary / Index M mega-: Meaning and Definition of Find definitions for: mega- Pronunciation: [key] var. of(megalith); also the initial element in units of measure that are equal to one million of the units denoted by the base word (megahertz). Symbol: M&hasp; Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Meg megabit Related Content Daily Word Quiz: abominable Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language