High Quality Content by WIKIPEDIA articles! Headlight flashing refers to the act of either briefly switching on the headlights of a car, or of momentarily switching between a headlight`s high beams and low beams, in an effort to communicate with another driver or drivers. This signal can be intended to convey a variety of messages, including a warning to other drivers of road hazards or of speed traps, and it can also be a form of aggressive driving. The legality of headlight flashing varies by jurisdiction.