There is only one way to describe her:
Very slim, friendly to guys, pretty average face, but her ass is the most interesting thing about her. Its PERFECT, in all ways, and compared to most women/girls around. Usually the ass is wrapped in flexible tight grey pants, which excellently
outline the ass girl's beautiful
curve. Ass girls have the best ass in a given area (mostly in colleges), so the plural term is quite rare by itself.
In addition, this term is used to refer to a
ass goddess whose name you dont know.