Definition
A unit of rotational speed indicating the number of complete turns a rotating component makes in one minute. In a piston-engine airplane, RPM most commonly refers to the rotational speed of the engine crankshaft (and, on a fixed-pitch propeller, the propeller itself, since they turn together). It is displayed on the tachometer and is the primary power setting reference for fixed-pitch propeller airplanes.
Plain English
How many full turns something makes every minute. In an airplane, it usually means how fast the engine and propeller are spinning.
Context Anchor
Seen on the engine speed gauge and in procedures that call for a specific power setting, including power-off approach practice.
Derivation
From Latin 'revolvere' meaning 'to turn or roll back.' A revolution is one complete turn, so revolutions per minute is simply a count of full turns made each minute.
Why Pilots Care
Proper RPM keeps the engine inside safe operating limits and helps control descent rate and airspeed when power is reduced.
Intuition Check
RPM is a rate, not a total count. It means turns per minute, not how many times the engine has turned since it started.
Example Sentence 1
On the 90° power-off approach, the pilot reduced power to idle RPM and allowed the airplane to glide toward the runway.
Example Sentence 2
In cruise the pilot set 2300 RPM for best fuel economy and engine longevity.