Cubitus meaning : The ulna. One of the major veins of the insect wing, between the media and the postcubitus; the vein running along the dorsal edge of the discal cell. The elbow, or the corresponding joint in the forelimb of a quadruped. The forearm; the arm from the elbow to fingertip, or the corresponding portion of a jointed limb of an animal that uses the limb for locomotion or grasping.