/ 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: simian Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language