external oblique muscle

(anatomy) A flat muscle on each side that form the outer layer of the lateral walls of the abdomen, that have aponeuroses extending medially to ensheathe the rectus muscles and fusing in the midventral line in the linea alba, and that act to compress the abdominal contents and to assist in expelling the contents of various visceral organs (as in urination, defecation, parturition, and expiration).