The act of knocking on a door with the sole intent of performing fellatio on the occupant.
You: "Someone knocked 6 time on my door while I was in the shower. That seems a little much for the UPS guy, who do you think it was?"
Me: "Maybe it was one of your Cockknockers coming over to give you a BJ"
You: "isn't it common knowledge to not just drop by?"
Me: "To normal people, not cockknockers"