A tiny, revealing skirt that chicks wear when they want the attention of some boners.
Dude, check out that hottie over there in the boneskirt, i wanna hit that.
A huge erection. Not at half staff, this kind of boner is in full salute. If up for too long you get light headed.. The kind that garners positive or shocked reactions.
"Daym look at yr boneskirt, that thing is a monster!"