Cars & Driving
- noun an instrument in the instrument panel, electronically operated by the ignition system, which indicates engine rpm with an analogue or digital read-out; red areas indicate dangerous engine operating speeds.
- A device for measuring rotation speed. Usually refers to revolutions per minute (RPM) of a revolving shaft.
- A device or instrument which measures and indicates angular velocity. When graduated in revolutions per minute, also called RPM meter. Its abbreviation is tach.