The Collaborative International Dictionary of English v.0.48:

Reotrope \Re"o*trope\ (-tr?p), n. (Physics)
   See Rheotrope.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rheotrope \Rhe"o*trope\, n. [Gr. "rei^n to flow + ??? to turn.]
   (Elec.)
   An instrument for reversing the direction of an electric
   current. [Written also reotrope.]
   [1913 Webster]