\Plas"tron\, n. [F. plastron breastplate, plastron, LL.
plastra a thin plate of metal. See {Plaster}.]
1. A piece of leather stuffed or padded, worn by fencers to
   protect the breast. --Dryden.
3. (Anc. Armor) An iron breastplate, worn under the hauberk.
3. (Anat.) The ventral shield or shell of tortoises and
   turtles. See {Testudinata}.
4. A trimming for the front of a woman's dress, made of a
   different material, and narrowing from the shoulders to
   the waist.