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]

The Collaborative International Dictionary of English v.0.48:

Encaustic \En*caus"tic\, n. [L. encaustica, Gr. ? (sc. ?): cf.
   F. encaustique. See Encaustic, a.]
   The method of painting in heated wax, or in any way where
   heat is used to fix the colors.
   [1913 Webster]

WordNet (r) 3.0 (2006):

encaustic
    n 1: a paint consisting of pigment mixed with melted beeswax; it
         is fixed with heat after application