Pertaining to the abdomen or belly; situated in or on the abdomen: as, abdominal ventral fins.In ichthyology, having ventral fins under the abdomen and about the middle of the body: as, an abdominal fish. See Abdominales.plural Certain imaginary lines drawn to divide the surface of the abdomen into regions, as given below.retains the name of epigastric; its lateral portions (4 4) are the right and left hypochondriac regions; the middle part of the umbilicalis called the umbilical region, while its lateral portions (5 5) are the right and left lumbar regions; the middle portion of the hypogastric zoneis called the hypogastric region, but sometimes the pubic region, while its lateral portions (6 6) are called the right and left iliac (or inguinal) regions. The adjoining region of the thigh, below the fold of the groin, is properly excluded.External, a similar oblong opening in the fascia of the obliquus externus abdominis (external oblique muscle of the abdomen), further down and nearer the mid-line of the body. These rings are respectively the inlet and outlet of the inguinal canal. Also called inguinal rings.n. One of the Abdominales (which see).