A spotty ass also known as buttknee, or in a more descriptive way, acne on your bum that you get from sitting down. This is caused from not smoothingyour bum, some are even born with it. Name is Butt Acne
An extremely obese person's knees that are exposed and create a likeness to a butt view from the layers of extra skin that dimple and come together while standing or walking or the posterior image created when an extremelyobese person is standing still and wearing shorts or a skirt