What is "plastron"

Plastron \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.

c.1500, from Middle French plastron "breastplate," from Italian piastrone, augmentative of piastra "breastplate, thin metal plate" (see piaster). As an animal part, from 1813; as an article of dress, 1876.

n. 1 The nearly flat part of the shell structure of a tortoise or other animal, similar in composition to the carapace. 2 (context fencing English) A half-jacket worn under the jacket for padding or for safety. 3 An ornamental front panel on a woman's bodice. 4 A film of air trapped by specialized hairs against the body of an aquatic insect, and which acts as an external gill.

1. n. the ornamental front of a woman's bodice or shirt

2. the front of man's dress shirt

3. a metal breastplate that was worn under a coat of mail

4. a large pad worn by a fencer to protect the chest

5. (zoology) the part of a turtle's shell forming its underside