Comité Consultatif International Téléphonique et Télégraphique (International Telegraph and Telephone Consultative Comittee), an organization that sets international communications standards. It was founded in 1956 as a result of the merging of CCIR (International Radio Consultative Committee) and CCIT (International Telegraph Consultative Committee). The organization (its parent organization, actually) is nowadays known as ITU. CCITT has defined important standards of which most are still being used: Group 3 fax protocol, communications protocols V.21, V.22, V.32 and so on, V.42 error detection standard for high speed modems, the X.25 packet switching protocol, the universal email protocol X.400 and many others.
For more information, consult the ITU web site: http://www.itu.int/