A trendline breakout occurs when the price moves decisively above a downward sloping trendline that has been acting as resistance by connecting lower highs. This indicates that the previous selling pressure is weakening and buyers are gaining strength, potentially signaling a shift in trend from bearish to bullish. A strong breakout is usually supported by higher trading volume and a clear close above the trendline, rather than just an intraday spike. After the breakout, price may retest the broken trendline, which can then act as new support; if it holds, it increases the probability of further upward momentum.