Source : Free On-Line Dictionary of Computing

software laser
     
        An optical laser works by bouncing photons back and forth
        between two mirrors, one totally reflective and one partially
        reflective.  If the lasing material (usually a crystal) has
        the right properties, photons scattering off the atoms in the
        crystal will excite cascades of more photons, all in lockstep.
        Eventually the beam will escape through the partially
        reflective mirror.
     
        One kind of {sorcerer's apprentice mode} involving {bounce
        message}s can produce closely analogous results, with a
        {cascade} of messages escaping to flood nearby systems.  By
        mid-1993 there had been at least two publicised incidents of
        this kind.
     
        [{Jargon File}]