stop order

An order to a broker to buy or sell a stock when it reaches a specified level of decline or gain in price.

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".

Investopedia Says:
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 then 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, trendlines, swing highs, swing lows or other key support or resistance levels.

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Order to a securities broker to buy or sell at the Market Price once the security has traded at a specified price called the stop price. A stop order may be a Day Order, a Good-Till-Canceled Order or any other form of time-limit order. A stop order to buy, always at a stop price above the current market price, is usually designed to protect a profit or to limit a loss on a short sale (see Selling Short). A stop order to sell, always at a price below the current market price, is usually designed to protect a profit or to limit a loss on a security already purchased at a higher price. The risk of stop orders is that they may be triggered by temporary market movements or that they may be executed at prices several points higher or lower than the stop price because of market orders placed ahead of them. Also called stop-loss order. See also Gather in the Stops; Stop Limit Order; Stop Loss (stocks).

A direction by a customer to a stock broker, directing the broker to wait until a stock reaches a particular price and then to complete the transaction by purchasing or selling shares of that stock.