When you cum on a girl's stomach and rub it all around her body like lotion, like she's your bread you're buttering her with your nut.
"I nutter buttered my girlfriend last night and she has a really bad rash on her skin now"
Peeing after masturbation, or any sexual act consisting ejaculation for males, creates Pizz. A mixture thick, sticky mixture of Pee and Jizz.
Mark: Dude did Melissa give you a blow job last night?
Mike: Yea but I had to pee really bad and I think I accidentally Pizzed on her face...