Cockblock Definition

(vulgar, slang) To make impossible another's intended goal of sexual intercourse.

(vulgar, slang, by extension) To prevent someone from achieving a goal, aggressively getting in the way.

(slang) A person who deliberately or inadvertently makes impossible another's intended goal of sexual intercourse.

(slang, by extension) Something designed to prevent one from achieving a goal (e.g. an intentionally difficult level of video game).