—adj.
1 in excess of the normal number; extra.
2 (of a person) engaged for extra work.
3 (of an actor) appearing on stage but not speaking.
—n. (pl. -ies)
1 an extra or unwanted person or thing.
2 a supernumerary actor.
3 a person engaged for extra work.
Etymology: LL supernumerarius (soldier) added to a legion already complete, f. L super numerum beyond the number
Useful english dictionary. 2012.