ATR (Average True Range)

Average true range (ATR) is a technical analysis volatility indicator originally developed by J. Welles Wilder, Jr. for commodities. The indicator does not provide an indication of price trend, simply the degree of price volatility. The average true range is an N-day exponential moving average of the true range values. Wilder recommended a 14-period smoothing.

http://en.wikipedia.org/wiki/Average_true_range