Abdomen
AB'DOMEN, or ABDO'MEN, noun [Latin perhaps abdo and omentum.]
1. The lower belly or that part of the body which lies between the thorax and the bottom of the pelvis. It is lined with a membrane called peritoneum, and contains the stomach, liver, spleen, pancreas, kidneys, bladder and guts. It is separated from the breast internally by the diaphragm, and externally, by the extremities of the ribs. On its outer surface it is divided into four regions - the epigastric, the umbilical, the hypogastric and lumbar.
2. In insects, the lower part of the animal, united to the corslet by a thread. In some species, it is covered with wings, and a case. It is divided into segments and rings, on the sides of which are small spiracles by which the insect respires.