Source : Free On-Line Dictionary of Computing

Address Resolution Protocol
     
         (ARP) A method for finding a {host}'s
        {Ethernet address} from its {Internet address}.  The sender
        broadcasts an ARP {packet} containing the {Internet address}
        of another host and waits for it (or some other host) to send
        back its Ethernet address.  Each host maintains a {cache} of
        address translations to reduce delay and loading.  ARP allows
        the Internet address to be independent of the Ethernet address
        but it only works if all hosts support it.
     
        ARP is defined in {RFC 826}.
     
        The alternative for hosts that do not do ARP is {constant
        mapping}.
     
        See also {proxy ARP}, {reverse ARP}.
     
        (1995-03-20)