1. Someone who performs death penalties; especially, a person who puts a condemned person to death: "Merrill was the official executioner of those who were convicted of murder."
2. A person or people who have completed a task or an assignment: "The two men were successful executioners of the project."
3. Someone who performs something; such as, an instrument used in producing a desired effect: "Marcy was a talented and successful executioner of classical music with the piano."