A manqueef is one of those sneaky farts that gets trapped in a dudes butt rack, and travels out underneath the balls, usually happens when sitting/laying in certain positions.
when you have a fart that doesnt have enough pressure to expel itself out from between your ass cheeks and you are forced to squeeze your ass cheeks together and cause the trapped fart bubble to expel from under your ball sack. usually results in a high pitched popping sound