Changing existing software code in order to improve the overall design. Refactoring normally doesn’t change the observable behavior of the software; it improves its internal structure. For example, if a programmer wants to add new functionality to a program, she may decide to refactor the program first to simplify the addition of new functionality in order to reduce technical debt. Refactoring is one of the original twelve extreme programming practices and is considered critical for incrementally maintaining technical quality on Agile development projects.
Related links: Refactoring