The part of the body below the thorax, containing the digestive organs and female reproductive organs: 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.

In anatomy, the third, posterior most major division of the body; belly, tummy: The abdomen is that part of a person's body between the thorax and the pelvis, but not including the back