The impression your rear end or ''butt'' leaves behind when you stand up from being in a seated position on a bed fitted with loose sheets, or a soft couch. It's the disturbance of the fabric of which you were previously seated whether it be a bunching of the sheets in a ''twist-like'' manner, or a simple butt imprint.
1) Person 1: Gets off bed after sitting on it for an extended period of time.
Person 2: Points at the bed, "YO, check out this kid's butt twist!"
2) A paranormal show, like ghost hunters:
"Is there anyone one in this room?"
Takes out infrared cam
"I can tell by the butt twist on that cushioned chair that there is a presence in this room besides myself."