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."