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]