A sloppy casserole involves three people. Preferably two girls and one gentleman. The casserole consists of feces, menstruation, and seminal fluids. They are combined on the chest of one of the ladies. It's sloppy because of the incredible mess it creates.
"Clint once gave a sloppy casserole to this chick I heard." - Rynoceros
"No way, are there leftovers?" - Ryan
poop, menstruation, and jizz all combined on the chest of a lucky lady. A man shits, then a female menstruates, and the guy finishes off on the shitty menstruation. After, the guy and the lady who didn't get crapped on laugh at the woman on the ground with the sloppy casserole on her chest.
HAHAHAHAHA that chick has sloppy casserole all over her! HAHAHAHAHAHHAA!