Breadcrumb Home > Dictionary > Index M mach number: Meaning and Definition of Find definitions for: mach' num"ber Pronunciation: [key] mach. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. machmeter macho ✖ Related Content Daily Word Quiz: restive Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language