/ Dictionary / Index M MI6: Meaning and Definition of Find definitions for: MI6 Pronunciation: (em'ī"siks'), [key] — n. the government's secret intelligence service. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. MI5 MIA Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language