1. Abdomen: 1 n the region of the body of a vertebrate between the thorax and the pelvis Synonyms: belly , stomach , venter Types: underbelly , underbody the soft belly or underside of an animal's body Type of: body part any part of an organism such as an organ or extremity n the cavity containing the major viscera; in mammals it is separated

2. Belly: 1 n the region of the body of a vertebrate between the thorax and the pelvis Synonyms: abdomen , stomach , venter Types: underBelly , underbody the soft Belly or underside of an animal's body Type of: body part any part of an organism such as an organ or extremity n the underpart of the body of certain vertebrates such as snakes or fish