"Kill" meant murder at the time the KJV was translated.

"Smite" and "slay" is lawful and/or accidental killing, and can mean anything from "justifiable homicide" to "involuntary manslaughter", depending on context.

Here's a link to Numbers 35, which lays down the rules regarding "manslayers" and "murderers."

https://www.biblegateway.com/passage/?search=Numbers+35&version=KJV

It breaks down the differences between involuntary manslaughter and death, and even discusses what we would refer to as premeditated first degree murder-

20 But if he thrust him of hatred, or hurl at him by laying of wait, that he die;

If the manslayer claims he killed someone unintentionally, he had to flee to one of six cities as outlined in the above chapter until he was either tried and convicted of his crimes (which required 2 or more witnesses) or until the current high priest died, at which point he was free to return to his native city.

"Kill" meant murder at the time the KJV was translated.

"Smite" and "slay" is lawful and/or accidental killing, and can mean anything from "justifiable homicide" to "involuntary manslaughter", depending on context.