A base is a term used by technical analysts to refer to a type of stock chart pattern. Base patterns indicate periods when a stock levels off or corrects after having advanced for a while; a base is just another term for a consolidation phase. Used properly, in conjunction with fundamental considerations such as sales, earnings and a host of other factors, a basing pattern can be used as an indicator of future price advances. There are several different base patterns such as the cup with handle, double bottom, saucer with handle, and flat base.
Go to the How to Buy Stocks link within IBD University to learn about identifying common base types.