Used in context of general equities. Order giving a broker a choice between two courses of action, either to buy or sell, never both. Execution of one course automatically eliminates the other. An example is a combination buy limit/ buy stop order, where the buy limit is below the current market and the buy stop is above. If the order is for one unit of trading, when one part of the order is executed on the occurrence of one alternative, the order on the other alternative is to be treated as cancelled. If the order is for an amount of more than one unit of trading, the number of units executed determines the amount of the alternative order to be treated as cancelled. Sometimes known as One Cancels the Other. Also see: Either-or order.