One Cancels Other OCO

OCO is an acronym for One Cancels Other.

This is typically used in the market where you only want one type of order to be filled and not the other.

If for example, you have a long position in the market and you are unable to manage the position you can place both a Stop and a Target order as OCO orders and when one of those are filled the other is canceled. This prevents you from getting put into an opposite (unwanted) position in the event that the market trades through one price and then the other.