When your banging a girl from on top, and get off and proceed to jerk as if to nut on her face, when your quickly turn around, and surprise her with poop instead!
I did a rolling brownout! "How?" While banging your little sister, she thought I was about to finish, I hopped over to her face, and when she shut her eyes SPLAT!... crapped all over her face.
When you are laying down, the girl squats on your face or chest, and starts pooping.
Timmy was so horny, he asks his girlfriend to give him a rolling brownout while he touched himself.