The Collaborative International Dictionary of English v.0.48:

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"nala.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ensiform \En"si*form\, a. [L. ensis sword + -form: cf. F.
   ensiforme.]
   Having the form of a sword blade; sword-shaped; as, an
   ensiform leaf.
   [1913 Webster]

   Ensiform cartilage, & Ensiform process. (Anat.) See
      Xiphisternum.
      [1913 Webster]