- a piece of plate armor for the upper part of the torso in front.
- Fencing. a quilted pad worn over part of the torso, for protection.
- an ornamental front piece of a woman’s bodice.
- the starched front of a shirt.
- Zoology. the ventral part of the shell of a turtle.
- the bony plate forming the ventral part of the shell of a tortoise or turtle
n.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.