damn brit lingo...call it a damn a$$. A bum is that begger on the street, or in so cal, the business man dressed as a bum who sits near the freeway on ramps who "will work for food."
i find that the most defining characteristic to a nice butt on a girl has to be the thighs that go with it. Rarely will you see a girl with nice thighs and a butt that is too big or small.