Source : Free On-Line Dictionary of Computing

failover
     
         Automatically switching to a redundant or
        standby server, system, or network upon the failure or
        abnormal termination of the currently-active server, system,
        or network (a "{hot standby}" or "{warm standby}").  Failover
        happens without human intervention.  This feature is usually
        built-in to expensive systems which must be available
        continuously.
     
        (2001-03-19)