any device for measuring speed, esp the rate of revolution of a shaft. Tachometers (rev counters) are often fitted to cars to indicate the number of revolutions per minute of the engine
tach in American English
(tæk)
noun
tachometer
tach in American English
(tæk)
noun
informal
tachometer
Word origin
[1925–30; by shortening]This word is first recorded in the period 1925–30. Other words that entered Englishat around the same time include: decibel, distinctive feature, dropout, off-line, runout