The Free On-line Dictionary of Computing (30 December 2018):

supervisor mode

   (Or "supervisor state") An execution mode on some processors
   which enables execution of all instructions, including
   privileged instructions.  It may also give access to
   different a address space, to memory management hardware
   and to other peripherals.  This is the mode in which the
   operating system usually runs.

   Opposite: user mode.

   (1995-02-15)