supernumerary
Concise Oxford English Dictionary © 2008 Oxford University Press:
supernumerary /ˌsuːpəˈnjuːm(ə)r(ə)ri/
▶adjective
- 1 present in excess of the normal or requisite number.
- 2 not belonging to a regular staff but engaged for extra work.
■ (of an actor) appearing on stage but not speaking.
– origin C17: from late L. supernumerarius ‘(soldier) added to a legion after it is complete’.
'supernumerary' also found in these Oxford entries:

