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DictionaryMachSpeed relative to sound
noun

Mach

MAHK/mɑːk/

Speed expressed as a multiple of the speed of sound.

The aircraft's instrument reads Mach 2.

A close-up aircraft Machmeter with its needle at 2.0, showing speed as a multiple of the speed of sound through an authentic instrument reading.
Etymology
machGermansurname of Ernst Mach

The name honors Austrian physicist Ernst Mach. A Mach number is a relative speed measure: it states how many times the speed of sound something travels.

In context

Progressive Discussions27:07
the saucer went from traveling at mach 4.3 greater than four times the speed of sound to a breezy mach 2.
Right-Wing Pastor Says the Poor Should Starve to Death-GOP Says Pope is Too Much Like Jesus

More examples

  • The jet reached Mach 1.
  • They compared different Mach numbers.
  • The display showed a lower Mach number.

Forms

Mach

Similar words

airspeed
Actual speed through air rather than its ratio to sound speed.
supersonic
Above Mach 1 rather than a numerical speed ratio.