An order to buy or sell a security when its price surpasses a particular point, thus ensuring a greater probability of achieving a predetermined entry or exit price, limiting the investor's loss or locking in his or her profit. Once the price surpasses the predefined entry/exit point, the stop order becomes a market order.

Also referred to as a "stop" and/or "stop-loss order."

Investors commonly use a stop order before leaving for holidays or entering a situation where they are unable to monitor their portfolio for an extended period. Stops are not a 100% guarantee of getting the desired entry/exit points. For instance, if a stock gaps down, the trader's stop order will be triggered (or filled) at a price significantly lower than expected. Traders who use technical analysis will place stop orders below major moving averages, trend lines, swing highs, swing lows or other key support or resistance levels.