A sentiment indicator that is derived by dividing the short interest by the average daily volume for a stock. This indicator is used by both fundamental and technical traders to identify the prevailing sentiment the market has for a specific stock.
Also known as the "short ratio". 
Investopedia Says:
This ratio provides a number that is used by investors to determine how long it will take short sellers, in days, to cover their entire positions if the price of a stock begins to rise. The short interest ratio can also be applied to entire exchanges to determine the sentiment of the market as a whole. If an exchange has a high short interest ratio of around five or greater, this can be taken as a bearish signal, and vice versa.
Related Links:
Have you ever correctly predicted a stock's decline or wondered how to be profitable in a bear market? Find out how and the risks involved. Short Selling Tutorial
Find out how this figure can be a real eye-opener on market sentiment of a given stock. Short Interest: What It Tells Us
For a record-holding stock trader, CANSLIM is the formula that identifies this magic mix. Trader's Corner: Finding The Magic Mix Of Fundamentals And Technicals




