Source : Webster's Revised Unabridged Dictionary (1913)

Rhodopsin \Rho*dop"sin\, n. [Gr. "ro`don rose + "w`ps eye.]
   (Physiol.)
   The visual purple. See under {Visual}.

Source : WordNet®

rhodopsin
     n : a red photopigment in the retinal rods of vertebrates;
         dissociates into retinene by light [syn: {visual purple},
          {retinal purple}]