A trendline breakout happens when price decisively moves beyond a well-respected trendline that was acting as support in an uptrend or resistance in a downtrend, signaling a potential change in momentum or trend continuation. When price closes above a falling trendline, it suggests buyers are gaining control; when it breaks below a rising trendline, sellers are taking over. A valid breakout is usually supported by strong candle close, increased volume, or follow-through price action, showing conviction rather than noise. Often, price may retest the broken trendline before continuing in the breakout direction, which helps confirm the move and offers a better risk-reward setup.