A mumu is a formless, very loose-fitting garment that completely covers the body from neckline to ankles, usually with some sort of print as coloration, and almost always in soft, bright, and/or vibrant colors. Mumus have the advantage of being very easy to put on and take off. It is hard for some people to tell the diference between a mumu and a dress.
Zippy the Pinhead wears one.

It has been rumoured that John Sununu wears a mumu with a tutu, but those rumors are unsubstatiated.

'Mumu' is occasionally spelled 'muu-muu'.