This word is used for fat people that smell horribly bad. It doesn't matter if their asses are clean, as long as they smell bad, its always considered to be buttstank.
This amazing and talented young womanapparently has the most powerful farts on the planet; I watched her doing the buttstroke the entire length of the high school gym pool!
When a person is born with the parts to form a butt (butt cheeks) but no flesh ever properly forms in it, so that the prson doesn't have the natural roundness of a butt and are therefore forced to sit on the extension of their thighs for lack of a natural butt. Or in simpler terms- lack of butt meat.
Hold on, is that Crystals's thighs or just her vestigial buttsack that's creepingfrom the top of her jeans when she bends over?