/ Dictionary / Index M MGB: Meaning and Definition of Find definitions for: MGB Pronunciation: [key] the Ministry of State Security in the U.S.S.R. that functioned as the government's secret-police organization from 1946–53. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mGal mgd 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