Someone who accedes to some act, now especially a crime; one who contributes as an assistant or instigator to the commission of an offense.
Accompanying as a subordinate; additional; accessory; especially, uniting in, or contributing to, a crime, but not as chief actor. See accessory.
An assistant to another person, especially to a superior or more important person.
In literature, theatre/theater, etc., a good foil of the protagonist, a character who helps emphasize the traits of the main character.