Breadcrumb Home > Dictionary > Index M MDT: Meaning and Definition of Find definitions for: MDT Pronunciation: [key] mean downtime. Mountain daylight time. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mdse. me ✖ Related Content Daily Word Quiz: umbrage Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language