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.
1."that ass girl in my physics 1410 lab.. oh man, I wanna touch that ass! Ooh! But she is too good. A goddess. Damn, I wanna cry! that ass is so big and lucious! And she is so in shape.. and, oh God, look at her, she is standing with her back to me.. Oh, God! Dont make her bend, I WILL EXPLODE. Damn, I cant even focus on the lab! Oh no, she is leaving..."
2."did you see the ass girl today, dude?"