A trendline breakdown occurs when the price of a stock falls below an established trendline support that was previously connecting multiple higher lows in an uptrend. This breakdown signals that the buying momentum is weakening and sellers are starting to gain control of the price movement. When the trendline is decisively broken, it often indicates a possible trend reversal or the beginning of a corrective phase. Traders closely watch such breakdowns because they may lead to further downside movement, especially if the price fails to reclaim the trendline and it starts acting as a resistance leve