A one-cancels-the-other (OCO) order is a trading instruction where the execution of one order automatically cancels a second order.
A one-cancels-the-other (OCO) order combines a pair of different trading order types, such as a limit order and a stop order, allowing simultaneous placement of stop loss and profit objectives for positions.
OCO orders are conditional orders in trading used by traders to simultaneously place two orders: a primary order and a secondary order. They operate so that if one order is fulfilled, the other is automatically canceled.
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Source: https://cointelegraph.com/explained/what-is-a-one-cancels-the-other-oco-order-explained