Exact HitTest?

How would you make a hitTest, so it would only work when one thing touches the other, not just their bounding boxes?

I’m making a sideshooter kind of game, and when you move, the plane rotates in that direction, but the bounding box just gets bigger and everything crashes into it.

Erm, I guess what I’m trying to say, is how do you get hitTest to work like a button, the way it does it by exact pixels?

(I’m absolutely horrible at explaining things, if you couldn’t tell, XD)