Source : Webster's Revised Unabridged Dictionary (1913)

Thoracic \Tho*rac"ic\, a. [Cf. F. thoracique.] (Anat.)
   Of or pertaining to the thorax, or chest.

   {Thoracic duct} (Anat.), the great trunk of the lymphatic
      vessels, situated on the ventral side of the vertebral
      column in the thorax and abdomen. See Illust. of
      {Lacteal}.

Source : WordNet®

thoracic duct
     n : the major duct of the lymphatic system