The Collaborative International Dictionary of English v.0.48:

Terephthalic \Ter`eph*thal"ic\, a. [Terebene + phthalic.]
   (Chem.)
   Of, pertaining to, or designating, a dibasic acid of the
   aromatic series, metameric with phthalic acid, and obtained,
   as a tasteless white crystalline powder, by the oxidation of
   oil of turpentine; -- called also paraphthalic acid. Cf.
   Phthalic.
   [1913 Webster]