Source : Free On-Line Dictionary of Computing

power save mode
     
         A feature of a component or subsystem designed
        to actively reduce its power consumption when not in use.
        Almost any electronic device might benefit from having a power
        save mode but the most common application is for portable
        computers which attempt to conserve battery life by
        incorporating power saving modes in the {CPU}, display, disks,
        printer, or other units.
     
        (1995-10-14)