To make a mounted disk, device, or file system inaccessible to the operating system, typically before physically disconnecting it. Before unplugging the USB stick, be sure to unmount it.
To get off or dismount from a horse, bicycle, or other conveyance. The cyclist unmounted at the checkpoint to refill his water bottle.
To remove something from its supporting mount or setting; detach from its frame, backing, or support. The curator carefully unmounted the painting from the wall.