[syn: excess, extra, redundant, spare, supererogatory, superfluous, supernumerary, surplus]
The Collaborative International Dictionary of English v.0.48:
Supernumerary \Su`per*nu"mer*a*ry\, a. [L. supernumerarius: cf.
   OF. supernum['e]raire, F. surnum['e]raire. See Super-, and
   Numerary, Number.]
   1. Exceeding the number stated or prescribed; as, a
      supernumerary officer in a regiment.
      [1913 Webster]
   2. Exceeding a necessary, usual, or required number or
      quality; superfluous; as, supernumerary addresses;
      supernumerary expense. --Addison.
      [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
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]
WordNet (r) 3.0 (2006):
supernumerary
    adj 1: more than is needed, desired, or required; "trying to
           lose excess weight"; "found some extra change lying on
           the dresser"; "yet another book on heraldry might be
           thought redundant"; "skills made redundant by
           technological advance"; "sleeping in the spare room";
           "supernumerary ornamentation"; "it was supererogatory of
           her to gloat"; "delete superfluous (or unnecessary)
           words"; "extra ribs as well as other supernumerary
           internal parts"; "surplus cheese distributed to the
           needy" [syn: excess, extra, redundant, spare,
           supererogatory, superfluous, supernumerary,
           surplus]
    n 1: a person serving no apparent function; "reducing staff is
         difficult because our employees include no supernumeraries"
    2: a minor actor in crowd scenes [syn: supernumerary, spear
       carrier, extra]