A type of option order which gives the trading crowd one opportunity to take the other side of the trade. After being announced, the order will be either partially or totally filled with any remaining balance immediately cancelled. An IOC order, which can be considered a type of day order, cannot be used as part of a GTC order since it will be cancelled shortly after being entered. The difference between fill-or-kill (FOK) orders and IOC orders is that a IOC order may be partially executed.