What is "legacy system"

n. (context computing English) An old computer system or application program that continues to be used because the user (typically an organization) does not want to replace or redesign it.

In computing, a legacy system is an old method, technology, computer system, or application program, "of, relating to, or being a previous or outdated computer system." Often a pejorative term, referencing a system as "legacy" often implies that the system is out of date or in need of replacement.