Someone with a face that makes them look as though they've just ate some poop. This can be just a funny face that someone is putting on temporarily for laughs, or for some unfortunate folks, a permanent disfigurement from birth. This look is achieved by having the upper lip slightly brought up near the nose and almost puckered, the nostrils flared, and in servere cases the eyes are slightly squinted and the brow is furled.
Larry: By the face tom always makes, you'd think he'd just ate some poop.
Barry: No man, don't make fun of him, he was born with a poopface.
Larry: Oh, so he doesn't actually eat bad tasting food all the time, he was just born like that?
Barry: Exactly, they're looking for a cure.