Today's Word of the Day means...
Any system for re-using backup media, e.g. magnetic tape. One extreme would be to use the same media for every backup (e.g. copy disk A to disk B), the other extreme would be to use new media every time. The trade-off is between the cost of buying and storing media and the ability to restore any version of any file. One example is the Grandfather, Father, Son (GFS) scheme.