The Collaborative International Dictionary of English v.0.48:

Interrupter \In`ter*rupt"er\, n.
   1. One who, or that which, interrupts.
      [1913 Webster]

   2. (Elec.) A device for opening and closing an electrical
      circuit; a vibrating spring or tuning fork, arranged to
      make and break a circuit at rapidly recurring intervals,
      by the action of the current itself. [Also spelled
      interruptor.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

interrupter
    n 1: a device for automatically interrupting an electric current