A game played when taking a shit. It is played by guessing the shape of the turd deposited in the toilet and then comparing it to an architectural shape template (usually hanging on a chain from the toilet paper holder) by standing over the bowl and viewing the turd through the template. Shapes include parallelogram, trapezoid, circle, square, etc. You have to know your sphincter pretty well to be good at the game. If the turd is pelletized then the game becomes similar to guessing the number of jelly beans in a jar.
I once played a game of Shapes and actually won when I shit a trapezoid. I'm sure it was a lucky guess.