stinky grimbus

A stinky grimbus is a sexual act, where you buy a Hotwheels car of an American, yellow school bus. You ingest a ton of laxatives and insert the school bus inside your sphincter.
You then your partner to thrash your bum with his/her strap-on or meat sword until you shit yourself, ejecting shit inside yourself covering the school bus which is still inside you, in your liquidy doodoo. You then retrieve the school bus from your anus and find that it is now a dark brown instead if yellow and looking quite grim. A "grim-bus" and quite stinky

"Old-mate fell asleep first at the party, I think I'm gonna pump him full of laxatives and give him a stinky grimbus to wake him up."