The Free On-line Dictionary of Computing (19 January 2023):

Large Installation Systems Administration

   (LISA) The USENIX systems administration conference.  It is
   now more general that its title suggests.  It is sponsored and
   organised by SAGE, the USENIX Systems Administrators Guild.

   (ftp://ftp.sage.usenix.org/pub/sage/).

   (1996-01-02)