n. pl. tho·rax·es or tho·ra·ces (thôrə-sēz′)
1. The part of the human body between the neck and the diaphragm, partially encased by the ribs and containing the heart and lungs; the chest.
2. A part in other vertebrates that corresponds to the human thorax.
3. The second or middle region of the body of certain arthropods, including the insects and most crustaceans, lying between the head and the abdomen.
[Middle English, from Latin thōrāx, breastplate, chest, from Greek.]
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