root

root n.  [UNIX] 1. The {superuser} account (with user name
   `root') that ignores permission bits, user number 0 on a UNIX
   system.  The term {avatar} is also used.  2. The top node of the
   system directory structure (home directory of the root user).
   3. By extension, the privileged system-maintenance login on any
   OS.  See {root mode}, {go root}, see also {wheel}.