Can my boss do this to me?

I've been working as a student worker for a little over a year now. At first, I enjoyed the job quite thoroughly. Starting a couple months ago, however, he's begun to touch me. He's been squeezing my nipples or slapping me in the balls whenever I say something stupid or mess up, and sometimes for no reason at all. He's even wrapped his arm around my neck once or twice. I've told him to stop, I don't like it, and I figured it's sexual harassment... He says it's only sexual harassment if the touching is sexual in nature... Is he right in this instance? Can he do this to me? It's really been bothering me.