When someone gets flames coming off their butt due to:
1. Eating an extremely hot curry
2. Having un-lubed anal sex
3. Someone has put a flammable substance on your butt and your ass begins burning and blisters your butthole
"That curry was so hot, when i crapped it created a buttfire. My goddamn ring is blistered."
"Your such an idiot, why didn't you use lube?! Now your buttfire has melted the condom to my cock and your butthole."
"Haha, yeah we made a buttfire on Paul, it was cold last night."