The term refactoring is often used incorrectly. When refactoring, you are merely changing the structure of the code. If the logic and/or signature of the code in question changes, then this does not qualify as refactoring. This is a change; most likely a breaking change.
If I'm changing the structure of the code (refactoring), then I don't ever change its behavior at the same time. If I'm changing the interface by which some logic is invoked, I never change the logic itself at the same time.
– Kent Beck
A safe refactoring is one that is guaranteed to not accidentally break the code. Other changes that aren't intended to actually change the behavior of the code but could do it accidentally are considered unsafe refactoring. These usually involve changes to the private areas of the code that aren't directly exposed to consumers of your application.