scum bag
n : a person who is deemed to be despicable or contemptible;
"only a rotter would do that"; "kill the rat"; "throw the
bum out"; "you cowardly little pukes!"; "the British call
a contemptible person a `git'" [syn: rotter, dirty dog,
rat, skunk, stinker, stinkpot, bum, puke, crumb,
lowlife, so-and-so, git]