blinker boy 

A person who moronically drives down the street or highway with his or her turn signal on, making other drivers think he or she wants to change lanes, when in fact, he or she simply has forgotten to disengage the turn signal from a lane change many minutes or even hours ago.

I slowed down to let that Isuzu Trooper into my lane but it turned out he was just a blinker boy.

blinker boy by RachWho? August 30, 2008