The Collaborative International Dictionary of English v.0.48:

Blinker \Blink"er\, n.
   1. One who, or that which, blinks.
      [1913 Webster]

   2. A blinder for horses; a flap of leather on a horse's
      bridle to prevent him from seeing objects as his side
      hence, whatever obstructs sight or discernment.
      [1913 Webster]

            Nor bigots who but one way see,
            through blinkers of authority.        --M. Green.
      [1913 Webster]

   3. pl. A kind of goggles, used to protect the eyes form
      glare, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

blinker
    n 1: a light that flashes on and off; used as a signal or to
         send messages [syn: blinker, flasher]
    2: a blinking light on a motor vehicle that indicates the
       direction in which the vehicle is about to turn [syn:
       blinker, turn signal, turn indicator, trafficator]
    3: blind consisting of a leather eyepatch sewn to the side of
       the halter that prevents a horse from seeing something on
       either side [syn: winker, blinker, blinder]
    v 1: put blinders on (a horse)