It is when for instance in an uptrend one bar is bullish but the next bar opens at or above the close of the last bar and pushes down so that it closes below the low of the bar. Get what I'm saying? It is when a bar fully engulfs the bar before it by covering it, it is a bearish signal the one I was talking about but it would be bullish if you flipped everything I said ( for instance down trend, first bar down, second bar engulfs by trading up, that would be bullish)
Hope that speeds it up