A person who is dense, oblivious, or otherwise unaware that a girl has a crush on him. This person is generally male and, as the term states, attends Shippensburg University. Play on "Shithead".
May also be used to describe anyone with generally idiotic, annoying or immature behavior.
John acted like a ShipHead towards Sarah, making fun of her and acting like a jerk, to cover up the fact that he liked her. Too bad he didn't realize that she liked him too!