1873, irregular shortening of rotator (see rotate (v.)), originally in mathematics. Mechanical sense is attested from 1903; specifically of helicopters from 1930.
there are horizontal rotors on a helicopter or compressor rotors in a jet engine
rotgut
Rothschild
Rotifera
rotisserie
rotogravure
rotor
Rototiller
rotten
rottenness
rotter
Rottweiler
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