Source : Webster's Revised Unabridged Dictionary (1913)

Thiophthene \Thi*oph"thene\, n. [Abbreviated from
   thionaphthene.] (Chem.)
   A double thiophene nucleus, {C6H4S2}, analogous to
   thionaphthene, and the base of a large series of compounds.
   [Written also {thiophtene}.]