You are
fucking doggie style. You pull out, jizz on the
asshole, pee on top of the jizz, then you let him/her
fart and spray it all over you.
You- "
Dude, I was fucking this chic last night and I jizzed on her
asshole and covered it in
piss!".
friend- "What'd she do bro?"
You- "She farted on me man!?!?!?"
friend- "Bro, you got skunked!!"