Source : Webster's Revised Unabridged Dictionary (1913)

Metasternum \Met`a*ster"num\, n. [Pref. meta- + sternum.]
   1. (Anat.) The most posterior element of the sternum; the
      ensiform process; xiphisternum.

   2. (Zo["o]l.) The ventral plate of the third or last segment
      of the thorax of insects.