A system software component that is external to the operating system kernel. If the phrase is used to refer to the operating system itself, it is redundant because an operating system "is" software.

An operating system that is designed for a server. Normally, it is a complete operating system with file, task and job management; however, with some earlier products, it was a separate component that ...

If you don't know what the Linux desktop operating system is, or if you're new to it, Jack Wallen's quick explainer will get you up to speed. Linux. What is it? At one point in time it was a niche ...