STOCK: A magical piece of paper that is worth $33.75 until the moment you buy it. It will then be worth $8.50.
BOND: What you had with your spouse until you pawned his/her golf clubs to invest in Amazon.com.
BROKER: The person you trust to help you make major financial decisions. Please note the first five letters of this word spell Broke.
BEAR: What your trade account and wallet will be when you take a flyer on that hot stock tip your secretary gave you.
BULL: What your broker uses to explain why your mutual funds tanked during the last quarter.
MARGIN: Where you scribble the latest quotes when you're supposed to be listening to your manager's presentation.
SHORT POSITION: A type of trade where, in theory, a person sells stocks he doesn't actually own. Since this also only ever works in theory, a short position is what a person usually ends up being in (i.e. "The rent, sir? Hahaha, well, I'm a little short this month.").
COMMISSION: The only reliable way to make money on the stock market, which is why your broker charges you one.
YAK: What you do into a pail when you discover your stocks have plunged and your broker is making a margin call.