A varient on the word slag, but not used as an exact synonym. Instead, it is an insult to someone who is being annoying, stupid or you just dislike.
(Playing poker)
Ben: "O.k so if I have a straight but with the ten, jack, queen, king, ace, is that a royal straght?"
Dudley "you fucking slag muffin."
Ben: "O.k so if I have a straight but with the ten, jack, queen, king, ace, is that a royal straght?"
Dudley "you fucking slag muffin."
by Dudley Brewbags May 28, 2008