Source : Webster's Revised Unabridged Dictionary (1913)

Ounce \Ounce\, n. [F. once, fr. L. uncia a twelfth, the twelfth
   part of a pound or of a foot: cf. Gr. ? bulk, mass, atom. Cf.
   2d {Inch}, {Oke}.]
   1. A weight, the sixteenth part of a pound avoirdupois, and
      containing 437? grains.

   2. (Troy Weight) The twelfth part of a troy pound.

   Note: The troy ounce contains twenty pennyweights, each of
         twenty-four grains, or, in all, 480 grains, and is the
         twelfth part of the troy pound. The troy ounce is also
         a weight in apothecaries' weight. [Troy ounce is
         sometimes written as one word, {troyounce}.]

   3. Fig.: A small portion; a bit. [Obs.]

            By ounces hung his locks that he had. --Chaucer.

   {Fluid ounce}. See under {Fluid}, n.

Ounce \Ounce\, n. [F. once; cf. It. lonza, Sp. onza; prob. for
   lonce, taken as l'once, fr. L. lynx, Gr. ?, or an (assumed)
   fem. adj. lyncea, from lynx. Cf. {Lynx}.] (Zo["o]l.)
   A feline quadruped ({Felis irbis, or uncia}) resembling the
   leopard in size, and somewhat in color, but it has longer and
   thicker fur, which forms a short mane on the back. The ounce
   is pale yellowish gray, with irregular dark spots on the neck
   and limbs, and dark rings on the body. It inhabits the lofty
   mountain ranges of Asia. Called also {once}.

Source : WordNet®

ounce
     n 1: a unit of apothecary weight equal to 480 grains or one
          twelfth of a pound [syn: {troy ounce}, {apothecaries'
          ounce}]
     2: a unit of weight equal to one sixteenth of a pound or 16
        drams or 28.349 grams [syn: {oz.}]
     3: large feline of upland central Asia having long thick
        whitish fur [syn: {snow leopard}, {Panthera uncia}]