Source : Webster's Revised Unabridged Dictionary (1913)

Thebaine \The*ba"ine\, n. [So called from a kind of Egyptian
   opium produced at Thebes.] (Chem.)
   A poisonous alkaloid, {C19H21NO3}, found in opium in small
   quantities, having a sharp, astringent taste, and a tetanic
   action resembling that of strychnine.