Source : Webster's Revised Unabridged Dictionary (1913)

Blinder \Blind"er\, n.
   1. One who, or that which, blinds.

   2. (Saddlery) One of the leather screens on a bridle, to
      hinder a horse from seeing objects at the side; a blinker.

Source : WordNet®

blinder
     n : blind consisting of a leather eye-patch sewn to the side of
         the halter that prevents a horse from seeing something on
         either side [syn: {winker}, {blinker}]