A sexual position in which the receiver is lying down face up, the giver places his scrotum on the top of their head like a cap, with their penis going down over the nose, like the nose guard of a helmet, ending with the head in the receivers mouth.
Can also be done with the receiver sitting and the giver standing/squatting above them.
Guy #1: dude when she laid down I so planted my junk on her head and gave her a nice sweaty skullcap!
Guy #2: Nice man! *offers hand for high five*