Boorish is the adjective, not the person. It describes rude, clumsy, uncultured behaviour: a boorish remark, boorish manners, a boorish joke. It means “like a boor” — showing little feel for the people in the room. Though the old noun often pointed at men, the adjective can describe anyone’s behaviour, or a comment, or a way of speaking. It is fairly formal, and it is a real slap at someone’s manners, not a light tease. It is not a synonym of boring (“dull, not interesting”), even though the two can look alike on the page.