Definition of: plastron

(plas′trən) noun
1. An ornamental addition to the front of a woman's dress, reaching from the throat to the waist.
2. A leather shield worn on the breast by fencers.
3. Zool. The under or ventral part of the shell or armor of a turtle or tortoise: also plas′trum.
4. The starched bosom of a man's shirt.
5. An iron breastplate worn under a coat of mail. [<F, orig. a breastplate <Ital. piastrone, aug. of piastra a breastplate]
—plas′tral adjective