Definitions of blinker:

• noun:   a light that flashes on and off; used as a signal or to send messages
• noun:   a blinking light on a motor vehicle that indicates the direction in which the vehicle is about to turn
• noun:   blind consisting of a leather eye-patch sewn to the side of the halter that prevents a horse from seeing something on either side
• verb:   put blinders on (a horse)