The Collaborative International Dictionary of English v.0.48:

Thiophene \Thi"o*phene\, n. [Thio- + phenyl + -ene.] (Chem.)
   A sulphur hydrocarbon, C4H4S, analogous to furfuran and
   benzene, and acting as the base of a large number of
   substances which closely resemble the corresponding aromatic
   derivatives.
   [1913 Webster]