资料来源 : Webster's Revised Unabridged Dictionary (1913)

Rheocrat \Rhe"o*crat\, n. [Gr. "rei^n to flow + kratei^n to
   rule.] (Elec.)
   A kind of motor speed controller permitting of very gradual
   variation in speed and of reverse. It is especially suitable
   for use with motor driven machine tools.