quadratus Definition

any of several skeletal muscles more or less quadrilateral in outline

a small flat muscle of the gluteal region that arises from the ischial tuberosity, inserts into the greater trochanter and adjacent region of the femur, and serves to rotate the thigh laterally

levator labii superioris

a quadrilateral-shaped muscle of the abdomen that arises from the iliac crest and the iliolumbar ligament, inserts into the lowest rib and the upper four lumbar vertebrae, and functions especially to flex the trunk laterally

a muscle of the sole of the foot that arises by two heads from the calcaneus, inserts into the lateral side of the tendons of the flexor digitorum longus, and aids in flexing the toes

a deep muscle of the forearm passing transversely from the ulna to the radius and serving to pronate the forearm

a facial muscle arising from the lower margin of the orbit and inserting into the muscular substance of the upper lip which it elevates —called also quadratus labii superioris