Mixing one's cum with sand, cement, and gravel that creates a form of concrete with cum instead of water. Great for building, just not for one's family or friends.
Damn bro, y'all are using concrete to pave roads, while I'm using cumcrete. Yeah, I was banned from the sperm bank.
My roommate is a bastard. He left cumcrete on the bathroom counter by the toilet. I thought it was toothpaste until a tried to wipe it up with a wet cloth and almost puked from the smell.