The Collaborative International Dictionary of English v.0.48:

Encaustic \En*caus"tic\, a. [L. encausticus, Gr. ?, fr. ? to
   burn in; ? in + ? to burn: cf. F. encaustique. See Caustic,
   and cf. Ink.] (Fine Arts)
   Prepared by means of heat; burned in.
   [1913 Webster]

   Encaustic painting (Fine Arts), painting by means of wax
      with which the colors are combined, and which is
      afterwards fused with hot irons, thus fixing the colors.


   Encaustic tile (Fine Arts), an earthenware tile which has a
      decorative pattern and is not wholly of one color.
      [1913 Webster]