What is Executioner?

Legal Definition
A judicial executioner is a person who carries out a death sentence ordered by the state or other legal authority, which was known in feudal terminology as high justice. Note that the role of an executioner should not be confused with that of an executor, a person who is responsible for executing (meaning "following through on") an assigned task or duty.
-- Wikipedia
Legal Definition
The name given to him who puts criminals to death, according to their sentence; a hangman.

2. In the United States, executions are so rare that there are no executioners by profession. It is the duty of the sheriff or marshal to perform this office, or to procure a deputy to do it for him.
-- Bouviers Law Dictionary
Legal Definition
The name given to him who puts criminals to death, according to their sentence; a hangman.
-- Black's Law Dictionary
Legal Definition
One who executes a death sentence.
-- Ballentine's Law Dictionary