An example is a Unix server where multiple remote users have access (such as via Secure Shell) to the Unix shell prompt at the same time. Another example uses multiple X Window sessions spread across multiple terminals powered by a single machine - this is an example of the use of thin client.
The complementary term, single-user, is most commonly used when talking about an operating system being usable only by one person at a time, or in reference to a single-user software license agreement. Multi-user operating systems such as Unix sometimes have a single user process available for emergency maintenance.
US Patent Issued to Microsoft on May 17 for "System and Methods for Exchanging User Interface Data in a Multi-User System" (Washington Inventors)
May 21, 2011; ALEXANDRIA, Va., May 21 -- United States Patent no. 7,945,942, issued on May 17, was assigned to Microsoft Corp. (Redmond, Wash...