A concept originated by Dan Fitzpatrick to describe the first break of a powerful, prolonged trend. A stock that breaks sharply below an established up sloping support line will often rebound and resume the prior uptrend. Many traders will see this break and bounce as an anomaly -- a "one off" that doesn't mean anything. Only later, when the uptrend ends and the stock reverses will the trader see that the first break of the trend was indeed a sell signal. It was a shot across the bow that should have been heeded.