Definitions
1.NounThe nearly flat part of the shell structure of a tortoise or other animal, similar in composition to the carapace.
2.NounA half-jacket worn under the jacket for padding or for safety.
3.NounA man's shirt-bosom.
4.NounAn ornamental front panel on a woman's bodice.
5.NounA breastplate.
6.NounA film of air trapped by specialized hairs against the body of an aquatic insect, and which acts as an external gill."The plastron of a diving beetle is not directly a source of oxygen, but acts as a gill, acquiring oxygen from the surrounding water."