From The Collaborative International Dictionary of English v.0.48 [gcide]:
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]
From WordNet (r) 3.0 (2006) [wn]:
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)