While performing anal sex the receptive partner suffers from explosive diarrhea, resulting in a shit spray all over the penetrative partner.
Karen gave Nathan a massive chocolate explosion when they hooked up last night. She had some bad Mexican food... and he was so drunk, he didn't manage to clean himself up until this afternoon.
When eating someones asshole they let a fart go and fecal matter flies into your mouth.
"I was eating this girls ass out and she let a shart go"
"Haha you got a Chocolate Explosion"