Agent noun of cockblock: one who cockblocks.
To make or attempt to make another's intended goal of sexual intercourse impossible.
To prevent someone from achieving a goal, aggressively getting in the way (e.g. an intentionally difficult level of video game).
The act of cockblocking.
A person who cockblocks.
A cockblock (or cock block) is a slang term for an action, whether intentional or not, that prevents someone from having sex. Such behavior is said to be motivated by jealousy or competitiveness, although it is sometimes accidental or inadvertent.