The noise made by butt cheeks flapping together as gas is expelled violently. This usually occurs after consuming several bean burritos, drinking a warm coke and jumping on a trampoline.
George sure is noisy today. He has a terrible case of flutterbutt
The fondling of one's butt crack in a rhythmic flute like manner, often in a joking situation, occasionally in a sensual one.
Sean wrestled Andrew down to the ground and gave him a flutterbutt