Mach number
noun
ˈmäk- 
: a number representing the ratio of the speed of a body (such as an aircraft) to the speed of sound in a surrounding medium (such as air)
Word History
Etymology
Ernst Mach †1916 Austrian physicist
First Known Use
1937, in the meaning defined above
Medical Definition
Mach number
noun
ˈmäk-
: a number representing the ratio of the speed of a body to the speed of sound in a surrounding medium (as air)
a Mach number of 2 indicates a speed that is twice that of sound