[joshuacc]

In English, the term murder usually means something closer to "the intentional unjustified killing of a sapient* being."

If it's not intentional, it's not murder, it's an accident. If it is justified, then it isn't murder, it's e.g., self-defense. If the creature killed isn't sapient, then it isn't murder, but it might be animal cruelty.

Note that in order for it to be intentional, the killer must also meet some criteria for sapience, but that's not necessarily the same as being human. For example, in English translations of the Bible, Jesus refers to Satan as "a murderer from the beginning." (John 8:44)

[tialaramex]

It is not justifiable to intentionally kill people. It is to be expected that some forms of self defence will often - even usually - kill the other party, but that's not intentional killing. Likewise, armed police are trained to shoot to incapacitate opponents. Yes, shooting a person in the centre of mass will sometimes kill them, but, that's not the intent of doing it.

This is maybe less obvious if your government intentionally kills its own citizens for some reason and you've found it important to draw a moral distinction between "We pay government officials to deliberately kill people" and "Murder" but I have no problem saying that's the same thing, stop doing that.

[mongol]

I think you may have left out explaining your asterisk?

I have not heard the definition to be about a sapient being. I always thought it would need to be a human killing a human. Perhaps in fantasy novels it can be a dwarf killing an orch, but in the real world I don't think anything else qualifies. If we include AI in this definition, we put AI above animals, which I think is a stretch for the forseeable future.