1.the under portion of the shell of a turtle or tortoise that is made up of several, often hinged, bony plates joined to the carapace by bridges located between the animal's legs
2.a tuft of water-repellent hairs on the bodies of some insects that live in water, having the function of trapping air bubbles and acting as an external gill
3.a leather-covered pad for protecting the chest, worn by professional fencers
4.a steel breastplate worn as part of medieval armour beneath a chain-mail tunic
plastrons