Definition 1 of 2
Plain English Meaning
The spinning part of a machine. In helicopters it's the big set of blades on top. In an engine it's the shaft and wheels that spin inside. In a magneto or generator it's the spinning magnet that produces electrical current.
Full Definition
The rotating assembly of an aircraft, engine, or machine that produces lift, thrust, compression, or electrical output through its motion. In a helicopter, the rotor is the system of rotating blades that generates lift and directional control. In a turbine engine, it is the spinning shaft assembly carrying the compressor and turbine wheels. In a magneto or generator, it is the rotating component that induces in the surrounding stationary windings.