1) when you are taking a shower and have especially dry skin and the skin rolls off into these little spongy wet skin balls
2) the little bit of water at the bottom of the shower when you are done that is not quite clear and is full of aforementioned dry-skin-balls. essentially, dead skin cells mixed with shower water.
A name to call someone when you have nothing else to call them. The definition varies depending on what the user intends for the meaning to be based on the context in which it is used.