The Collaborative International Dictionary of English v.0.48:

Porcelain \Por"ce*lain\, n. (Bot.)
   Purslain. [Obs.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Porcelain \Por"ce*lain\ (277), n. [F. porcelaine, It.
   porcellana, orig., the porcelain shell, or Venus shell
   (Cypr[ae]a porcellana), from a dim. fr. L. porcus pig,
   probably from the resemblance of the shell in shape to a
   pig's back. Porcelain was called after this shell, either on
   account of its smoothness and whiteness, or because it was
   believed to be made from it. See Pork.]
   A fine translucent or semitransculent kind of earthenware,
   made first in China and Japan, but now also in Europe and
   America; -- called also China, or China ware.
   [1913 Webster]

         Porcelain, by being pure, is apt to break. --Dryden.
   [1913 Webster]

   Ivory porcelain, porcelain with a surface like ivory,
      produced by depolishing. See Depolishing.

   Porcelain clay. See under Clay.

   Porcelain crab (Zool.), any crab of the genus Porcellana
      and allied genera (family Porcellanid[ae]). They have a
      smooth, polished carapace.

   Porcelain jasper. (Min.) See Porcelanite.

   Porcelain printing, the transferring of an impression of an
      engraving to porcelain.

   Porcelain shell (Zool.), a cowry.
      [1913 Webster]

WordNet (r) 3.0 (2006):

porcelain
    n 1: ceramic ware made of a more or less translucent ceramic

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "porcelain":
   adobe, biscuit, bisque, bowl, brick, cement, ceramic ware,
   ceramics, china, clay, crock, crockery, enamel, enamelware,
   firebrick, glass, jug, pot, pottery, refractory, tile, tiling, urn,
   vase