The farting sound made while fucking someone either in the vagina or ass.
As the penis plunges in and out of the vagina or anus, a farting noise is made sounding similar to one that comes from the anus when flatulence occurs.
John: "Damn, me and Jessie were going hard at it all night!"
Dave: "Wow! Really?"
John: "Yup, so hard that I even heard a fuck fart!"
In the sexual act of anal sex the person farts on the other person
we were doing anal and she fuck farted on me