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1.
Slapping your (usually) left hand to your forehead as you lower your head to make quick contact with each other. Often done in response to someone doing or saying something stupid.

-A similar response to "Here's your sign........"
Person 1: "So no shit, there I was in the middle of the street, and some guy nearly ran me over!"

Person 2: *head smack*
by RocCityGoddess May 12, 2010