metasternum

from The Century Dictionary.

• noun In anatomy, the hindmost segment or last sterneber of the breast-bone; the xiphisternum, in man represented by the xiphoid cartilage or ensiform appendage.
• noun In entomology, the sternite of the metathorax; the median part of the postpectus.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Anat.) The most posterior element of the sternum; the ensiform process; xiphisternum.
• noun (Zoöl.) The ventral plate of the third or last segment of the thorax of insects.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy The most posterior element of the sternum; the ensiform process; xiphisternum
• noun zoology The ventral plate of the third or last segment of the thorax of insects.