MachPronunciation: /mɑːk, mak/ (also Mach number)Definition of Mach noun the ratio of the speed of a body to the speed of sound in the surrounding medium. It is often used with a numeral (as Mach 1, Mach 2, etc.) to indicate the speed of sound, twice the speed of sound, etc.. Origin: 1930s: named after Ernst Mach (see Mach, Ernst)Mach in other Oxford dictionaries Definition of Mach in the US English dictionary
