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}.