Spoon is the biggest cockblocker of them all.

Terrible. Some chick cockblocker screwed me big time

Paul is a total cock blocker. That guy is like a giant cock blocking robot developed in a secret fucking government lab. I was about to hook up with Lily and he ruined all my hard work.

"damn, this bitch is cock blocking me at every turn, tim can you take one for the team?"
"I'll take down that cock blocker, now run free unhindered my freind, go deep!"

1.) you could be at a bar talking to the best looking girl in the joint, and this girl might be all about you too, but then your drunk buddy who happens to be a blocker rolls up on the scene and starts falling all over the place, making you look like an asshole and scaring her away. That's a cock blocker.

2.) you might be in a bedroom with a girl about to get a piece and then all of the sudden, your buddy starts banging away at the door for no reason. He just wants to figure out a way for it be as hard as possible for you to get some. That's a cock blocker

examples courtesy of TwanDiggity

Why are these whores being such cockblockers! I saw him first!

Jon- So can i get your number?
Allsion-Su-
Cock blocker- So, jon, told her about your AIDS yet? i dont think she'll like that!
Allison- oh wow! cya!
Jon-dick...