This is when a man puts his penis between the butt cheeks of the 'reciever' rubbing their penis up and down this is called a buttwank. The man then whaps his shit covered cock just as he is about to cum and slaps his nob end in the recievers face. This then leaves a nob like shit stain on their forehead like a mushroom.
Tom whap'd his nob between alex's round cheeks and rub furiously. He pulled it out rather quickly tapped Alex on the shoulder and then slap'd his shitty nob end in his face.
"WoW ouch you gave me a fat buttcicle nob slap it's actually left a fat imprint."