Dome Blocker
Similar to the meaning of a person who "cock blocks," except this arrangement of "dome" and "blocker" sounds a lot cooler, than cock blocker. A person who interferes, or gets in the way, of somebody scoring on a female of their personal and sexual interests.
Hey Ryan, don't be such a dome blocker to Kevin! You know he likes Barbara and all, and he can't have you trying to steal her away from him.