One of several potentially awkward sounds created by the body's interaction with air, this one the result of suction from when the lumbar curve of the back is pressed flat against a smooth surface and then lifted, making a loud fart-like sound. Back farts most often occur when having sex on linoleum or when shifting about in a tanning bed.
J: T and I were doing the grown-up in stealth mode on that big mahogany table in the conference room last night, and I pulled this massive back fart.
A: I hate when that happens. Were you embarrassed?
J: Yeah, but only because the janitor heard it and opened the door.
A: Zut! what did you do?
J: I told him to drop trou -- daisy chain!