Source : Webster's Revised Unabridged Dictionary (1913)

Croton \Cro"ton\ (kr?"t?n), n. [Gr. ????, prop., a tick, which
   the seed of the croton resembles.] (Bot.)
   A genus of euphorbiaceous plants belonging to tropical
   countries.

   {Croton oil} (Med.), a viscid, acrid, brownish yellow oil
      obtained from the seeds of {Croton Tiglium}, a small tree
      of the East Indies. It is a most powerful drastic
      cathartic, and is used externally as a pustulant.

Source : WordNet®

croton oil
     n : viscid acrid brownish-yellow oil from the seeds of Croton
         tiglium having a violent cathartic action