From Longman Dictionary of Contemporary EnglishMachMach /mæk $ mɑːk/ noun [uncountable] 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
Examples from the Corpus
Mach• The plane can sustain a speed of Mach 3, or three times the speed of sound.Origin Mach (1900-2000) Ernst Mach (1838-1916), Austrian scientist 