Supernumerary \Su`per*nu"mer*a*ry\, n.; pl. {Supernumeraries}.
1. A person or thing beyond the number stated.
[1913 Webster]
2. 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.
[1913 Webster]