2. That section of the body that lies between the lower thorax or chest and the pelvis: The abdomen is the area of the body just below the diaphragm which contains the largest cavity in the body.
Also called belly (popular), venter, and stomach (incorrect). Derived from abdo, abdere, "to hide", and so probably originally referred to the "hidden part of the body".
Abdomen [Lat. from abdo, to hide.] A cavity commonly called the lower venter or belly: It contains the stomach, guts, liver, spleen, bladder, and is within lined with a membrane called peritoneum.
The abdomen is separated from the thorax by the diaphragm, a sheet of muscular tissue while the thorax is the part of the human body between the neck and abdomen, enclosed by the ribs and containing the heart and lungs.
The abdomen is separated anatomically from the chest by the diaphragm, the powerful muscle spanning the body cavity below the lungs.