A female who, "sex dances." This is the act of coming as close as you can to fucking on the dance floor while avoiding any actual contact.
This is usually followed by said girl either hooking up with her dance partner or getting ironically offended by a male dance partner's boner poking her in the back.
Girl 1: Jane is normally kind of a prude but when she gets on the dance floor she's kind of a whore.
Girl 2: Ya, she is definitely a sancer.