au·to·gi·ro also au·to·gy·ro 
(ô′tō-jīrō)
(ô′tō-jīrō)n. pl. au·to·gi·ros also au·to·gy·ros
An aircraft powered by a conventional propeller and supported in flight by a freewheeling, horizontal rotor that provides lift.
[Originally a trademark.]
autogiro