A person who is completely worthless, an inanimate object even. Less useful to society than than the chair he sits on. He will swindle his friends for anything including; being greedy about money or ditching you for puss.
Also a word that means shit, which is what they are a piece of.
Dillon- "yeah Justin completely swindled us to smash Jessica"
Jeremy- "yeah, he's bein a real scat lately"