A Female that has her vagina positioned further back towards her bum. These females generally have the sexiest body. Furthermore these females are the best to have Doggy Style sex with.
Kam: Oh my god, check that girl out!

Carl: That's a Arch Back Fanny Girl right there!
by ArchBackFannyGirlLover July 15, 2011
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What a girl does show off her butt if she has one, and be or try to be sexy. Typically girls with no ass do this as well to have some butt
Jessica has a flat ass so she arched all the way back when she saw hot guys.
by wowcanunot March 1, 2014
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