Turd Tube

This is the last couple of inches if the intestinal tract. It's where the turds come out. It's literally a tube for turds. And it sounds funny when you say it to someone who isn't expecting it.

Tell them I'll talk to them later. I have to go to the bathroom because my turd tube is full.

turd tubing

To exchange poop between two assholes by means of gaping and possibly tubes

Dude, I heard they were turd tubing last bight. Gross