scratch disk - Computer Definition
A hard disk used as a work space to store data temporarily. In highly computational applications such as editing large images or video, the scratch disk is used to hold the data being edited. Having one or more dedicated drives for scratch disks is the most efficient. However, if there is only one drive in the computer, a separate partition can be created on the drive that is not used for anything else, ensuring there is always available space. See scratch tape and scratchpad.