Source : Webster's Revised Unabridged Dictionary (1913)

Cardia \Car"di*a\, n. [NL., fr. Gr. ? heart, or upper orifice of
   the stomach.] (Anat.)
   (a) The heart.
   (b) The anterior or cardiac orifice of the stomach, where the
       esophagus enters it.

Source : WordNet®

cardia
     n : the opening into the stomach and that part of the stomach
         connected to the esophagus