Xiphisternum n. : The posterior segment, or extremity, of the sternum; -- sometimes called metasternum, ensiform cartilage, ensiform process, or xiphoid process.

Xiphisternum n. : The xiphiplastron.

Example:
At what approximate age does the Xiphisternum ossify?

Taxonomy
xiphoid process, free encyclopedia, Body of sternum, Bone, costal cartilage, birds, ribs, foramina, search, Unsourced, Lateral border, processus, xiphoideus, xiphisternum, extension, adult, fuses, body.

Defination from the web:
xiphisternum, is a small cartilaginous extension to the lower part of the sternum which is usually ossified in the adult human. ... By age 15 to 29, the xiphoid usually fuses to the body of the sternum with a fibrous joint. Unlike the synovial ...