Colon Colonisation

(Typically) Consensual anal sex between two parties that achieves deep, unprotected penetration with the aim of filling one (or both) party's colon with rich seminal fluid.

Guy 1: Hey, where's that £6.25 you owe me?
Guy 2: I'll get it, I swear.
Guy 1: You better, or you'd best start preparing yourself for colon colonisation.