The action of a trader/investor increasing a position in an asset when its price is heading in the direction that's opposite to what the investor/trader desires. This is generally not a wise investment decision because unless the asset begins to move in the desired direction, the investor's losses will increase.
An investor might add to a losing position instead of closing it because he or she gets emotionally attached to the asset and has a hard time accepting that it was a bad investment. once the trade moves substantially in the wrong direction, however, it may be time to consider closing out or re-evaluating the reason for having the position rather than putting more money at risk.