Plain English Meaning
How many times something spins all the way around in one minute.
Full Definition
A unit of rotational speed equal to the number of complete turns a rotating component makes in one minute. In aviation, it most commonly refers to the rotational speed of the engine crankshaft or, in turboprop and turbine engines, the propeller or compressor section.
Context Anchor
Seen on engine instruments, power-setting procedures, aircraft operating handbooks, and instructor discussions about engine operation.
Derivation
Revolution comes from the Latin revolvere, meaning to or turn around. One revolution is one complete turn. Per minute simply tells you the time window which those turns are counted.