ICMP

from The Free On-line Dictionary of Computing (8 July 2008)

Internet Control Message Protocol
ICMP

   <protocol> (ICMP) An extension to the {Internet Protocol} (IP)
   that allows for the generation of error messages, test
   packets, and informational messages related to IP.  It is
   defined in STD 5, {RFC 792}.

   (1999-09-18)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

ICMP
       Internet Control Message Protocol  [version 4] (TCP/IP, RFC 792,
Internet)