A very well-toned, and shapely booty. Denotes certain deliciouness. Can refer to male or female.
"Did you see Becky leave the room? That, my friend, is a rumptious."
by Daniel & Mike February 15, 2008
Posessing a large, juicy booty and other applicable curves.
Ooh, that Shakira is so rumptious. Did you see all that junk in her trunk?
by Cakehole August 16, 2005