Has various definitions. 1) On some exchanges, a market or limited price order that is to be executed in its entirety as soon as it is represented in the trading crowd, and, if not so executed, is to be treated as canceled. In this context, no partial fills are accepted, and the FOK order is treated as an IOC, AON order. 2) On other exchanges, a market or limit order that is to be executed by filling the number of shares made available by the first bid or offer, and then canceling any unfilled balance. In this context, a FOK order is treated as an instruction to fill what can be filled by hitting the first bid or offer, and cancel the rest. In this case partial fills are possible, and the FOK order is treated as an IOC, Any Part order. Because of the prevalence of interlisted stocks, the ability of a broker’s trading desk to direct trades to one exchange or another, and the different interpretations the order can have depending on which exchange the order is routed to, use of this type or order is discouraged. Instead, either an IOC AON, or an IOC Any Part, order will get the desired result regardless of the exchange.