It stands for minimum quantity order; a limit order to buy or sell a security (contract) that will only execute if a minimum amount of the security (contract) can be traded through the order. Otherwise, the order is cancelled. Orders with a specified minimum quantity will only execute on the basis of aggregating multiple orders if executions would occur simultaneously.

Minimum quantity orders may only be placed with a time-in-force (TIF) designation of immediate or cancel (IOC), while a minimum quantity on any other order will be rejected. As a rule, minimum quantity orders received prior to the market opening or after market close will be not be filled.

An exchange will only honor a specified minimum quantity on orders routed through a network of global markets (affiliated markets) that are non-displayed or IOCs and will reject or not consider a minimum quantity on any other order.