The Collaborative International Dictionary of English v.0.48:

Vitrified \Vit"ri*fied\, a.
   Converted into glass.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Vitrify \Vit"ri*fy\, v. t. [imp. & p. p. Vitrified; p. pr. &
   vb. n. Vitrifying.] [F. vitrifier; L. vitrum glass +
   -ficare to make. See Vitreous, -fy.]
   To convert into, or cause to resemble, glass or a glassy
   substance, by heat and fusion.
   [1913 Webster]

WordNet (r) 3.0 (2006):

vitrified
    adj 1: (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]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "vitrified":
   backed, calcified, callous, calloused, case-hardened, crusted,
   crusty, crystallized, fossilized, granulated, hardened, hornified,
   incrusted, indurate, indurated, lapidified, ossified, petrified,
   reinforced, rigidified, sclerotic, set, solidified, steeled,
   stiffened, strengthened, toughened