A medical name for stool / shit / poop / crap / feces that has large portion of fat in it. It can be identified when your stool floats not sink for a while. Your body doesn't have the ability to absorb (malabsorbtion) all that fat in McDonald's sandwich and therefore it releases it out.
I: Man I ate from McDonald's yesterday and I had a steatorrhea.
II: Oh shit, what is steatorrhea?
I: It's a shit.
II: I know it is all crappy but what is steatorrhea?
I: It's fatty shit that floats.
II: Oh fuck, you piece of shit can't you see we eating.