someone who prevents others from pulling
(doing a mark)

Anyone or anything that gets in the way of you getting some. The cock-block can be male,female, or inanimate. Many cock-blocks can't get any themselves so they try to stop somebody else. If they ain't scorin' nobody's scorin'. No scene is too embarassing in their undying quest to prevent your action. If your buddy's a cockblock don't bring him or her.

Trying to prevent someone from getting a woman/piece of pussy that someone else is trying to get.

To prevent one's friend from scoring, usually by acting inappropriately in front of some sweet ass.

what harry potter does on the regular to ron and hermione, literally almost everyday

1. To interfere with a man's attempts to seduce a woman.

2. abbr. Cockblocker(n.)

When you're hanging out with a girl, and one of your friends tries their hardest to split you and the girl up as a joke. This makes your friend a cockblock.