(n.) Hence, specifically, an official communication, not made in person, but delivered by a messenger; as, the President's message.
(v.t.) To bear as a message.
Webster's Revised Unabridged Dictionary
(DoD) A narrowly focused communication directed at a specific audience to support a specific theme. (DoD) Any thought or idea expressed briefly in a plain or secret language and prepared in a form suitable for transmission by any means of communication.
Department of Defense Dictionary of Military and Associated Terms. 31 January 2011.