Multi user
Multi-user is a term that defines an operating system or application software that allows concurrent access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving the CPU idle while it waits for I/O operations to complete. However, the term "multitasking" is more common in this context.
An example is a Unix server where multiple remote users have access (via Telnet or SSH) to the Unix shell prompt at the same time. Another example uses multiple X sessions spread across multiple monitors powered by a single machine.

Management systems are implicitly designed to be used by multiple users, typically one system administrator or more and an End-user (computer science) community.

The opposite 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.