plas·​tron ˈpla-strən How to pronounce plastron (audio)
: a metal breastplate formerly worn under the hauberk
: a quilted pad worn in fencing to protect the chest, waist, and the side on which the weapon is held
: the ventral part of the shell of a tortoise or turtle consisting typically of nine symmetrically placed bones overlaid by horny plates
: a trimming like a bib for a woman's dress
: a thin film of air held by water-repellent hairs of some aquatic insects

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English speakers first borrowed French's word for a breastplate, plastron, as the name for the protective plate worn under a tunic of [chain mail](/dictionary/chain mail) by knights. In the 17th century, plastron was extended to the pad used to protect the torso of a fencer. Two centuries later, herpetologists appropriated the word for a slightly different type of protection: the underside of a turtle's shell, which consists typically of nine bones overlaid by horny plates. That was followed by the word's application in the world of fashion to coverings that adorn the front of a woman's bodice, such as a lacy bib, as well as to a man's separate or detachable starched shirtfront (which is typically worn under a jacket).

Examples of plastron in a Sentence

Recent Examples on the Web Her report noted the juvenile turtle had a few abrasions on its plastron, or shell, with an open hole or sore near a long crack near its back left flipper. Kori Rumore, Chicago Tribune, 20 July 2023 Box turtles get their name from the hinged plastron (lower shell). Arkansas Online, 20 June 2022 To fix the plastron, the center's veterinarian worked with her father, a professor at Marquette University School of Dentistry. Evan Frank, Milwaukee Journal Sentinel, 1 Nov. 2019 Feavel said the turtle was likely hit by a vehicle, which fractured the skull, carapace (top shell) and plastron (bottom shell). Evan Frank, Milwaukee Journal Sentinel, 1 Nov. 2019 The domed carapace covering the back of the animal is connected to the flat plastron on the underside of the animal by a bridge of bone. Hans-Dieter Sues, Smithsonian, 20 Aug. 2019 The origin of the plastron covering the underside of the turtle is less obvious. Hans-Dieter Sues, Smithsonian, 20 Aug. 2019 In all cases, the apes accessed the meat through the bottom of the carapace, breaking a part technically called the plastron. Douglas Main, National Geographic, 23 May 2019 The cotton poplin plastron shirt took 11 hours to make, according to the French house. Rosemary Feitelberg | Wwd,, 25 Apr. 2018

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'plastron.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


Middle French, from Old Italian piastrone, augmentative of piastra thin metal plate — more at piastre

First Known Use

circa 1507, in the meaning defined at sense 1a

Time Traveler
The first known use of plastron was circa 1507


Dictionary Entries Near plastron

Cite this Entry

“Plastron.” Dictionary, Merriam-Webster, Accessed 19 Jun. 2024.

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