Mach /mæk $ mɑːk/ noun [uncountable]
[Date: 1900-2000; Origin: Ernst Mach (1838-1916), Austrian scientist]
a unit for measuring speed, especially of an aircraft, in relation to the speed of sound. Mach 1 is the speed of sound, Mach 2 is twice the speed of sound etc:
a plane with a maximum speed of Mach 3

[TahlilGaran] Dictionary of Contemporary English ▲