A boor is a crude, rude person. Boors lack sophistication and manners.
Boors are worse than boring; they’re offensive and repulsive. To be a boor is to be an obnoxious, unsophisticated oaf. A boor would swear in church. A boor would talk too loudly on the train. A boor would get too drunk at a wedding reception. Boors lack manners and taste. When a boor is around, other people want to leave. If you have self-control and culture, you’ll never be accused of being a boor.