The Collaborative International Dictionary of English v.0.48:

Vitreous \Vit"re*ous\, a. [L. vitreous, from vitrum glass;
   perhaps akin to videre to see (see Vision). Cf. Varnish.]
   1. Consisting of, or resembling, glass; glassy; as, vitreous
      rocks.
      [1913 Webster]

   2. Of or pertaining to glass; derived from glass; as,
      vitreous electricity.
      [1913 Webster]

   Vitreous body (Anat.), the vitreous humor. See the Note
      under Eye.

   Vitreous electricity (Elec.), the kind of electricity
      excited by rubbing glass with certain substances, as silk;
      positive electricity; -- opposed to resinous, or negative,
      electricity.

   Vitreous humor. (Anat.) See the Note under Eye.

   Vitreous sponge (Zool.), any one of numerous species of
      siliceous sponges having, often fibrous, glassy spicules
      which are normally six-rayed; a hexactinellid sponge. See
      Venus's basket, under Venus.
      [1913 Webster]

WordNet (r) 3.0 (2006):

vitreous
    adj 1: of or relating to or constituting the vitreous humor of
           the eye; "the vitreous chamber"
    2: relating to or resembling or derived from or containing
       glass; "vitreous rocks"; "vitreous silica"
    3: (of ceramics) having the surface made shiny and nonporous by
       fusing a vitreous solution to it; "glazed pottery"; "glassy
       porcelain"; "hard vitreous china used for plumbing fixtures"
       [syn: glassy, vitreous, vitrified]