请教“outstanding ”是何意思。

我在很多地方发现outstanding这个单词，请教它在驱动程序中是什么意思。如：
IoInitializeRemoveLock initalizes a remove lock for a device object. A driver can use the lock to track outstanding I/O on a device and to determine when the driver can delete its device object in response to an IRP_MN_REMOVE_DEVICE request.

outstanding有个意思是“未完成的”。在这里，应当是未完成的的I\O操作。