Definition of rotor blade in US English:

rotor blade

noun

  • Each of the radiating arms of a rotor of a motor, dynamo, etc., which sweep out a circular area as they rotate; (Aeronautics) each of the arms of the rotor of a helicopter or other rotary-wing aircraft; (Engineering) each of the aerofoils fitted in rows to the rotor of a turbine.

Origin

Early 20th century.