Definition of mastic

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