Sounds kind of dirty, right? Actually, it's because of a clean visual that technical analysts use this term. Technical analysts like charts (hence their nickname of "chartists"), and they like to give certain patterns they see neat little names.

Such is the case with the double bottom, which looks on a chart like, well, a double bottom. Think of three mountains (on a chart reflecting a rise in values) separated by two valleys (representing dips in value). The troughs of the valleys, and the size of the first two peaks, are generally the same, so the chart looks like the letter 'W.' The appearance of those two valleys represents a double bottom.

So what? Well, if you're one of those folks who believes in the power of the charts, seeing a double bottom suggests a long-term trend is about to reverse. So, if a stock chart shows shares falling for several months, then seeing a double bottom, chances are good (according to the chartists) that the shares will rise. And vice versa.

But, beware: charts can be a great tool, but they're more art than science. Use any charts with caution.