plastron
plas.tron \'plas-tr*n\ n [MF, fr. OIt piastrone, aug. of piastra thin metal plate - more a]t PIASTER 1a: a metal breastplate 1b: a quilted pad worn in fencing practice to protect the chest 2: the ventral part of the shell of a tortoise or turtle consisting typical ly of nine symmetrically placed bones overlaid by horny plates 3a: a trimming like a bib for a woman's dress 3b: DICKEY