A gravestone doji pattern is a common reversal pattern used by traders to suggest that a bullish rally or trend is about to reverse. It can also be found at the end of a downtrend, but this version is much more rare. As you can see from the chart, on the day of the gravestone doji (shown within the black box), bearish traders realized that the price was pushed up to unjustifiably high levels so they send the price back up to where the stock opened. The close near the day's low suggests that supply is starting to outweigh demand again.
Investment dictionary. Academic. 2012.