Plain English Meaning

How many times something spins all the way around in one minute. In a typical small airplane, it tells you how fast the engine and propeller are turning.

Full Definition

A measure of rotational speed expressing how many full turns a rotating component completes in one minute. In piston-engine airplanes, RPM most commonly refers to the speed of the engine crankshaft (and, on a fixed-pitch propeller, the propeller itself), and is the primary indication of engine power output displayed on the tachometer.

Context Anchor

Seen on the tachometer and in power-setting instructions, especially during the takeoff roll when the pilot checks that the engine is producing the expected power.