when macd forms highs or lows that exceed the corresponding highs and lows on the price it is called a divergence a bullish divergence appears when macd forms two rising lows that correspond with two falling lows on the price this is a valid bullish signal when the long term trend is still positive 
some traders will look for bullish divergences even when the long term trend is negative because they can signal a change in the trend although this technique is less reliable image by sabrina jiang investopedia 2022