Source : Free On-Line Dictionary of Computing

off-line
     
         (Or "offline")
     
        1. Not directly connected to the computer (e.g., an off-line
        {tape drive}), or with connection suspended ("take the
        {printer} off-line").
     
        Contrast {background}, {on-line}.
     
        2. Not now or not here.  "Let's take this discussion
        off-line."  Specifically used on {Usenet} to suggest that a
        discussion be moved off a public {newsgroup} to {e-mail}.
     
        See also {off-line world}.
     
        [{Jargon File}]
     
        (1996-02-02)