As you browse Craigslist and Facebook swap sites and things of that nature, you come across three letters. POS. Once upon a time POS stood for Piece of S*** but, judging from what they're selling, you know that's not the case in this case. Those letters are popping up more and more. You don't know what they mean but you don't want to sound ignorant and ask. In case you're curious, we have the answer.