Source : Webster's Revised Unabridged Dictionary (1913)

Xiphiplastron \Xiph"i*plas"tron\, n.; pl. {Xiphiplastra}. [NL.,
   fr. Gr. xi`fos a sword + plastron.] (Anat.)
   The posterior, or fourth, lateral plate in the plastron of
   turtles; -- called also {xiphisternum}.