When two or more farts have joined aromatic forces in a specific area transforming into one smell that cannot be tolerated by any of the creators.
In a supermarket I released a fart in an isle loaded with people and immediately left the scene. When I returned to observe my victims I noticed there must have been a counter-fart because the area did not smell familiar... it smelled like fartsex.
The act of humping and pounding a sweaty anus with which hot, steaming, acidic fart gas jet pulses fourth into the humpers wide open nostrils. The smell of the gas is so pungent that the humpers nostrils burn and blister which, being that the humper is sadomasochistic, makes him/her blow his/her load.
"Damnit my home fries, that fart sex last night with your mother was fanstastical!"
One day Bart and Suzie went to a Mexican restaurant, they both had refryed beans. And later on that night they were both getting all kinds of feelings. They both had caught a bad case of Gas from the beans. They also wanted to try something waay more kinkier than usual. So Bart layed on his stomach without pants or underwear on. This turned Suzie waaay on. so she took off her pants and underwear and she layed upon Bart butt to butt. And by accident Bart farted into Suzie's ass. This actualy gave her an exciting feeing so then she farted in his. And this continued on through the night. There being fart sex.