The nearly flat part of the shell structure of a tortoise or other animal, similar in composition to the carapace.
A half-jacket worn under the jacket for padding or for safety.
A man's shirt-bosom.
An ornamental front panel on a woman's bodice.
A breastplate.
A 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.