Source : Webster's Revised Unabridged Dictionary (1913)

Mastic \Mas"tic\, n. [F., fr. L. mastiche, mastichum, Gr. ?, fr.
   ? to chew, because of its being used in the East for
   chewing.] [Written also {mastich}.]
   1. (Bot.) A low shrubby tree of the genus {Pistacia} ({P.
      Lentiscus}), growing upon the islands and coasts of the
      Mediterranean, and producing a valuable resin; -- called
      also, {mastic tree}.

   2. A resin exuding from the mastic tree, and obtained by
      incision. The best is in yellowish white, semitransparent
      tears, of a faint smell, and is used as an astringent and
      an aromatic, also as an ingredient in varnishes.

   3. A kind of cement composed of burnt clay, litharge, and
      linseed oil, used for plastering walls, etc.

   {Barbary mastic} (Bot.), the {Pistachia Atlantica}.

   {Peruvian mastic tree} (Bot.), a small tree ({Schinus Molle})
      with peppery red berries; -- called also {pepper tree}.

   {West Indian mastic} (Bot.), a lofty tree ({Bursera
      gummifera}) full of gum resin in every part.

Source : WordNet®

mastic
     n 1: an aromatic exudate from the mastic tree; used chiefly in
          varnishes
     2: a pasty cement used as an adhesive or filler