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.
Plain English
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.
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.
Derivation
From the Latin 'revolvere,' meaning to roll back or turn around. A 'revolution' is one complete turn of a rotating part. 'Per minute' simply states the time window being measured. Together, the phrase counts complete turns within sixty seconds.
Why Pilots Care
Engine RPM directly determines power output and thrust; achieving the target value is required for short-field takeoff performance and safe climb gradients.
Intuition Check
Revolutions per minute does not mean aircraft speed. It means how fast a rotating part, usually the engine or propeller system, is turning.
Example Sentence 1
After releasing the brakes, the pilot confirmed the engine was producing full takeoff RPM as the airplane accelerated down the runway.
Example Sentence 2
After liftoff the pilot reduced power to 2,400 revolutions per minute while maintaining the best-rate climb speed.