Source : Webster's Revised Unabridged Dictionary (1913)

Uncia \Un"ci*a\, n.; pl. {Unci[ae]}. [L. See {Ounce} a measure
   of weight.]
   1. (Rom. Antiq.) A twelfth part, as of the Roman as; an
      ounce.

   2. (Alg.) A numerical coefficient in any particular case of
      the binomial theorem. [Obs.]