Capitulation is when investors give up any previous gains in any security or market by selling their positions during periods of declines. Capitulation can happen at any time, but typically happens during high volume trading and extended declines for securities. A market correction or bear market often leads investors to capitulate or panic sell. The term is a derived from a military term which refers to surrender.
After capitulation selling, many traders think there are bargain buying opportunities. The belief is that everyone who wants to sell a stock for any reason, including forced selling due to margin calls, has already sold. The price should then, theoretically, reverse or bounce off the lows. In other words, some investors believe that capitulation is the sign of a bottom.
Looking at the chart, price has been on a steady decline until that day in Dec 10 when volume was almost 10M and price closed at the low of the day. Those who couldn't stand the pain threw in the towel and sold. Usually after those who had to sell have sold, price reverses.