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

multi-user

    A term describing an operating system or
   application program that can be used by several people
   concurrently; opposite of single-user.  Unix is an example
   of a multi-user operating system, whereas most (but not all)
   versions of Microsoft Windows are intended to support only
   one user at a time.

   A multi-user system, by definition, supports concurrent
   processing of multiple tasks (once known as "time-sharing")
   or true parallel processing if it has multiple CPUs.

   While batch processing systems often ran jobs for serveral
   users concurrently, the term "multi-user" typically implies
   interactive access.

   Before Ethernet networks were commonplace, multi-user
   systems were accessed from a terminal (e.g. a vt100)
   connected via a serial line (typically RS-232).  This
   arrangement was eventually superseded by networked personal
   computers, perhaps sharing files on a file server.  With
   the wide-spread availability of Internet connections, the idea
   of sharing centralised resources is becoming trendy again with
   cloud computing and managed applications, though this time
   it is the overhead of administering the system that is being
   shared rather than the cost of the hardware.

   In gaming, both on PCs and games consoles, the equivalent
   term is multi-player, though the first multi-player games
   (e.g. ADVENT) were on multi-user computers.

   (2009-11-23)