When you're fucking a chick doggy style, she's hanging her head over the toilet either, dry heaving or upchucking (vomiting).
Woman is drunk, you're drunk, you gotta get your nut. So, you enter her from behind even though she is starting to throw up, or upchucking, maybe she's got the dry heaves and nothing comes out of her mouth. You don't care as long as you get to upchuck fuck.
You're sitting on a toilet getting head and you fart. Similar to a Lumpkin.
I was at this killer party sitting on a toilet getting head from this chick. I thought I was having a Lumpkin, but it was only a Fluffkin.