plastron

Concise Oxford English Dictionary © 2008 Oxford University Press:
plastron /ˈplastrən/

▶noun

• 1 a large pad worn by a fencer to protect the chest.

  ■ historical a steel breastplate worn beneath a hauberk.

• 2 an ornamental front of a women's bodice, fashionable in the late 19th century.

  ■ a man's starched shirt front.

• 3 Zoology the part of a tortoise's or turtle's shell forming the underside.

  ■ a similar ventral plate in some invertebrate animals.

– derivatives
plastral adjective.

– origin C16: from Fr., from Ital. piastrone, augmentative of piastra ‘breastplate’.