Someone who brakes his or her car for no apparent reason. This
be driving in front
of you, or, God help you, may be the driver of the car in which you are currently driving.
TOM: (yelling out the window of his car) Hey! What
are you braking for? There's nothing in front
of you! Come on! Move it!
SAM: Tom, he's just a random braker, dude. His first
instinct is to brake. They suck...