The female equivalent of a tea bag. When a girl lowers her genitals onto the forehead, or top of head, of an unsuspecting victim.
Dude #1 - "Lauren passes out by 10 o'clock at EVERY party."
Dude #2 - "It's all good, Melissa just gave her a fish hat. When she finds a diamond shaped hickey on her forehead tomorrow morning, she'll learn her lesson."