cockblock

To make or attempt to make another's intended goal of romantic relationship or sexual intercourse impossible.

[T]o COCK BLOCK: to interfere with a male's attempt to 'win over' a female, even if the other male is not interested in the female himself.

Excitement surged through him and his groin tingled tight. He heard himself growling low in his throat. At his stop he considered staying on. Maybe she would get off without the dude. Cockblocking chump motherfucker.

To prevent someone from achieving a goal, aggressively getting in the way (e.g., an intentionally difficult level of a video game).

The act of cockblocking.

A person who cockblocks.