double up investment & finance definition

To purchase an equal number of additional shares when the price of a stock declines. For example, an investor who purchases 500 shares of a stock at $40 per share would double up by purchasing an additional 500 shares if the price of the stock drops. This investment technique can also be applied to short sales. The risk of doubling up is that a bad decision on an initial trade will be compounded when additional shares of the same stock are purchased. Imagine doubling up on high-tech stocks during the dot-com bust.