A market indicator used in technical analysis also known as ARMS, calculated as follows: Arms Index = ((# of advancing issues / # of declining issues) / (Total up volume / Total down volume)). A value of less than 1 is considered bullish, greater than 1 bearish. Triple witching - Once every quarter — on the third Friday of March, June, September, and December — options, index options, and futures contracts expire on the same day in the U.S. In the past, when they expired at the same hour of the day, trading could be extremely volatile. But in recent years, the timing has been adjusted so that they expire at different times throughout the day, somewhat reducing the potential frenzy of trading.