Typically a very embarrassing thing which ends "the mood" instantaneously, though some are the inverse and are actually aroused by the act.
Joe: "It went well, until the flatulatio incident. Guess we shouldn't have gone to Taco Bell for the first date."
Bob: "What'd she do? Freak out?"
Joe: "No, that was the worst part. She asked if I could do it again."
Bob: "Someone who likes flatulatio.. I'm not sure if you should run for the hills or jump on that."