Conforming to the basic architecture and principles of the Unix operating system. Unix-like operating systems, such as Linux, may be POSIX compliant, which means that applications communicate with the OS via a standard programming interface (API).The phrase "Unix-like operating system" is meant to exclude Unix operating systems such as Sun's Solaris and HP's HP-UX because they, as well as others, are compliant with one of the UNIX specifications governed by The Open Group. Any Unix operating system that does not comply is a Unix-like operating system. See Unix, Open Group and Single UNIX Specification.
Said of a computer operating system that behaves closely to Unix. Often used to describe systems which do not qualify for use of the Unix trademark.
"NetBSD provides its users with a free Unix-like system."
Said of a computer program having design principles consistent with those of Unix.
"This program is much more Unix-like: it operates on standard I/O instead of prompting the user for filenames."