TimeInForce.ImmediateOrCancel. It is used when the trader wants as much of the order executed quickly as possible but tolerates that some may not fill.
Immediate or Cancel (IOC)
Immediate or Cancel - An order instruction requiring immediate execution of as much of the order as possible; any portion not immediately filled is canceled. Unlike FOK, IOC allows a partial fill: the executable part is filled at once, and the rest is canceled. In automated trading code, an IOC order would be submitted with a time-in-force flag