A MACD (Moving Average Convergence Divergence) bearish crossover occurs when the MACD line (the shorter-term moving average) crosses below the signal line (the longer-term moving average). This event signals a potential shift in momentum towards a bearish or downward trend in the asset is price. Traders often use this crossover as a signal to consider selling or taking a bearish position in the market, as it suggests a weakening of the current upward trend.