That extra bit of semen that stays in your urethra post-ejaculation.
Dude, after banging my girlfriend, I took a piss and shot a massive cum cork
Dried plug of semen blocking proper urethral flow. Usually created if a man doesn't urinate after sex. Extremely painful, but temporary.
"I thought I had kidney stones for a sec there...turns out it was just a cum cork."
"That cum cork came flying out and landed on Jack's toothbrush."