When a parent is unknowingly cockblocking their kid by being home. The parent is at home, leaving the kid and his girlfriend with no place to get it on. Therefore the parent is obliviously cock blocking.
Matt's Friend: "Yo Matt, did Katie come over last night?"
Matt: "Yeah, but my parent were being complete obliviouscock blockers!"
Using your training in the deadly arts to move in, steal, and hook up with the person your buddy has been trying to hook up with all night. Basically a last second sneak-attack.
Dude why did you have to cock-block me like that right before bar close?
Sorry man but my cock-block kung fu has far surpassed yours young padowan