I. |süpə(r)|n(y)üməˌrerē, -ˌreri adjective
Etymology: Late Latin supernumerarius, from Latin super- + numerus number + -arius -ary
1. : exceeding the usual, stated, or prescribed number
a supernumerary tooth
extra ribs, as well as other supernumerary internal parts — Science News Letter
specifically : not enumerated among the regular components of a group and especially of a military organization or staff or of the line elements of a military organization
offered the supernumerary position of inspector general — J.S.Roucek
2. : exceeding what is necessary, required, or desired : superfluous
the redundant subheading and supernumerary asterisk — Punch
3. : being the more numerous
in any population with an unbalanced sex composition … a larger number of members of the supernumerary sex remains in this group — William & Mary Quarterly
II. noun
( plural supernumeraries )
1. : a supernumerary person or thing: as
a. : a person employed not for regular service but for use in case of need
b. : an individual in excess of the number authorized for a given military or naval unit
carried about two thousand men, including supernumeraries on a training course for sea experience — Stanley Rogers
c. : a person serving no apparent function
reducing them both to the role of irrelevant supernumeraries — J.C. Powys
d. : an inert added member of a chromosome set
2. : an actor employed to play a walk-on (as in a mob scene or spectacle)