The Collaborative International Dictionary of English v.0.48:

Decemvir \De*cem"vir\ (d[-e]*s[e^]m"v[~e]r), n.; pl. E.
   Decemvirs, L. Decemviri. [L., fr. decem ten + vir a man.]
   1. One of a body of ten magistrates in ancient Rome.
      [1913 Webster]

   Note: The title of decemvirs was given to various bodies of
         Roman magistrates. The most celebrated decemvirs framed
         "the laws of the Twelve Tables," about 450 B. C., and
         had absolute authority for three years.
         [1913 Webster]

   2. A member of any body of ten men in authority.
      [1913 Webster]