Source : Free On-Line Dictionary of Computing

major release
     
         A {release} of a piece of software which is not
        merely a {revision} or a {bug fix release} but which contains
        substantial changes (e.g., an overhaul of the {interface},
        change in compatibility).
     
        Traditionally, major releases are numbered as X.0; for
        example, WordPerfect 6.0 is a major release, significantly
        different from any previous version; whereas WordPerfect 6.1
        has only minor changes, and is, thus, only a {revision}.
     
        See also {major delivery}.
     
        (1996-08-04)