Source : Webster's Revised Unabridged Dictionary (1913)

Xiphisternum \Xiph"i*ster"num\, n.; pl. {Xiphisterna}. [NL., fr.
   Gr. xi`fos a sword + sternum.] (Anat.)
   (a) The posterior segment, or extremity, of the sternum; --
       sometimes called {metasternum}, {ensiform cartilage},
       {ensiform process}, or {xiphoid process}.
   (b) The xiphiplastron. -- {Xiph"i*ster"nal}a.

Source : WordNet®

xiphoid process
     n : smallest of the three parts of the breastbone; articulates
         with the corpus sternum and the seventh rib