Source : Webster's Revised Unabridged Dictionary (1913)

Hydantoin \Hy*dan"to*in\, n. [Hydrogen + allantion.] (Chem.)
   A derivative of urea, {C3H4N2O2}, obtained from allantion, as
   a white, crystalline substance, with a sweetish taste; --
   called also {glycolyl urea}.

Source : WordNet®

hydantoin
     n : any of a group of anticonvulsant drugs used in treating
         epilepsy