adj. & n.
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.
[ LL supernumerarius (soldier) added to a legion already complete, f. L super numerum beyond the number ]