A small object one places in the toilet after taking a shit that can sail around the poop and poopie water. Pooper Schooners can be made out of generally anything, usually things that are disposable and able to be flushed.
Always wash your hands if you want to keep your Pooper Schooner.
Mike: "Hey Richard, what are you doing with your toilet?"
Richard: "I'm playing with my Pooper Schooner, dude! Watch it go around my poop!"