The Collaborative International Dictionary of English v.0.48:

Rheomotor \Rhe"o*mo`tor\ (r[=e]"[-o]*m[=o]*t[~e]r), n. [Gr.
   "rei^n to flow + E. motor.] (Elec.)
   Any apparatus by which an electrical current is originated.
   [R.]
   [1913 Webster]