The definition of murder was "manipulated" around the time of the second world war to include the world "unlawful".
Find an old dictionary (circa 1930) and look up the definition of murder. It mentions only a "premediated killing".
This is an unpopular opinion, especially with the "perpetual war" that we have to endure, but if you kill another person regardless of the justification, even if it's your job, or they wronged you, then you are a murderer. That includes the people who perform the executions and all soldiers. Putting a label on it or changing semantics doesn't make it ok.
(This was downvoted immediately obviously by a supporter of murderers)