Message

In telecommunication, the term message has the following meanings:

Any thought or idea expressed briefly in a plain or secret language, prepared in a form suitable for transmission by any means of communication.
An arbitrary amount of information whose beginning and end are defined or implied.
Record information expressed in plain or encrypted language and prepared in a format specified for intended transmission by a telecommunications system.

(Source: from Federal Standard 1037C and from the Department of Defense Dictionary of Military and Associated Terms)