blinker

(noun) a light that flashes on and off; used as a signal or to send messages. Synonyms: flasher.

(noun) a blinking light on a motor vehicle that indicates the direction in which the vehicle is about to turn. Synonyms: turn signal, turn indicator, trafficator.

(noun) blind consisting of a leather eyepatch sewn to the side of the halter that prevents a horse from seeing something on either side. Synonyms: winker, blinder.

(verb) put blinders on (a horse).