one who blocks other guys cocks when trying to insert in vagina, or mouth of woman.

A male in a group of female friends who's job is to stop other males trying to score with the females in the group. Done purposely because the girls either already have a boyfriend or just don't want to be annoyed that night.

The cock-blocker can be either a male friend, or someone hired (almost like a bodyguard).

Popular methods of the cock-blocker include:
* Switching places with the female.
* Grinding with the offending male.
* Kissing the female to let the male know she is unavailable.
* Jumping in between the male and the female.
* Shoving the male, or squaring up to him.
* Warning him off with gestures.

A female (usually unattractive, or socially "defective") that stays with her more attractive friend at a party and "looks after" her friend, or just sometimes gets in the way of her friend socially. Often times a young (not necessarily) male would be after the friend.