A person of the female sex that is well used and may be "worn out" who also has a muffin top or a slight belly that hangs over the pant line. you often find them soliciting at walmart

a girl who gets around like an item from tim hortons and is also open 24 hours a day. slut

A person (or muffin) that acts sluttishly, similar to a skankcookie.

A muffin without its top on, ie. topless muffin

a slutmuffin is a literal joinging of the words slut and muffin to produce a humourous sounding insult

A muffin with extra flavor and icing.
More tempting than the regular type muffins :

Of, or pertaining to, the bastard child of a female whore.