OCO order. An order that states that if one part of the order is filled then the other part of the order is cancelled. For example, an investor can place a stop-loss order and a limit order on one stock as a one cancels other order. If the price of the stock declines then the limit order is cancelled and the stop order is executed in order to minimize losses. If the price of the stock increases then the stop order is cancelled and the limit order is executed.