Source : Free On-Line Dictionary of Computing

DRAM refresh
     
         The operation which cycles through a {DRAM} reading
        each row and writing it back again to compensate for the
        gradual leakage of charge from the {capacitors} which store
        the data.  This may be done by the {CPU} but is often done by
        a dedicated {memory controller}.
     
        (1997-02-23)