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.
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. ...