A civil designation for somebody who works in a group, association or public office, without forming part of the regular staff; those distinguished from numerary. (For example, supernumerary judges are those who help the regular judges when there is a surplus amount of work.)
A person or thing beyond what is necessary or usual; especially, a person employed not for regular service, but only to fill the place of another in case of need; specifically, in theaters, a person who is not a regular actor, but is employed to appear in a stage spectacle