Source : Free On-Line Dictionary of Computing

hack mode
     
         Engaged in {hack}ing.  A Zen-like state of total
        focus on The Problem that may be achieved when one is hacking
        (this is why every good hacker is part mystic).  Ability to
        enter such concentration at will correlates strongly with
        wizardliness; it is one of the most important skills learned
        during {larval stage}.  Sometimes amplified as "deep hack
        mode".
     
        Being yanked out of hack mode (see {priority interrupt}) may
        be experienced as a physical shock, and the sensation of being
        in hack mode is more than a little habituating.  The intensity
        of this experience is probably by itself sufficient
        explanation for the existence of hackers, and explains why
        many resist being promoted out of positions where they can
        code.  See also {cyberspace}.
     
        Some aspects of hackish etiquette will appear quite odd to an
        observer unaware of the high value placed on hack mode.  For
        example, if someone appears at your door, it is perfectly okay
        to hold up a hand (without turning one's eyes away from the
        screen) to avoid being interrupted.  One may read, type, and
        interact with the computer for quite some time before further
        acknowledging the other's presence (of course, he or she is
        reciprocally free to leave without a word).  The understanding
        is that you might be in {hack mode} with a lot of delicate
        state in your head, and you dare not {swap} that context out
        until you have reached a good point to pause.  See also
        {juggling eggs}.
     
        [{Jargon File}]
     
        (1996-07-31)