Chicken-winging is a complicated way to cop a feel, usually used as a last resort against a particularly resiliant bra. The man, after failing to go under or undo the bra during a makeout session, may reach his hand up the girls shirt and then down into the cup from the top. This results in an awkward bend in the elbow, and causes the arm to resemble a chicken wing. Hence, chickenwinging.
She had on this bad motherfucker of a bra. So I had to resort to chicken-winging.