Source : Webster's Revised Unabridged Dictionary (1913)

Rectifier \Rec"ti*fi`er\ (r?k"t?*f?`?r), n.
   1. One who, or that which, rectifies.

   2. Specifically:
      (a) (Naut.) An instrument used for determining and
          rectifying the variations of the compass on board
          ship.
      (b) (Chem.) A rectificator.

Source : WordNet®

rectifier
     n 1: electrical device that transforms alternating into direct
          current
     2: a person who corrects or sets right; "a rectifier of
        prejudices"