Definition
A unit 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, since they turn together). On constant-speed propeller installations, engine RPM and propeller RPM are governed separately, and the tachometer typically displays propeller RPM.
Plain English
How many times something spins all the way around in one minute. In a small airplane, it usually means how fast the engine — and on simpler aircraft, the propeller — is turning.
Context Anchor
Seen on the engine-speed gauge and in engine starting, warm-up, and checklist procedures.
Derivation
Revolution comes from a Latin word meaning to roll back or turn around. That helps because one revolution is one complete turn, and RPM counts how many of those turns happen in one minute.
Why Pilots Care
Engine RPM must rise to specific values during start to confirm ignition and oil pressure; incorrect readings can indicate flooding, starter issues, or other problems.
Analogy
If a bicycle wheel makes 60 full turns in one minute, it is turning at 60 RPM. An airplane engine is measured the same way, just at much higher speeds.
Intuition Check
RPM does not mean engine power by itself. It means how fast the engine or propeller is turning.
Example Sentence 1
After starting the engine, the pilot set the throttle to about 1,000 RPM to let the oil warm up.
Example Sentence 2
The pilot set 2400 RPM with the throttle for the recommended cruise power setting.