Having the form of a smooth and shallow depression; socketlike; -- applied to several articular surfaces of bone; as, the glenoid cavity, or fossa, of the scapula, in which the head of the humerus articulates.

adjective, Greek glene = socket, and eidos = shape or form.

the portion of the scapula (shoulder blade) that forms the cup segment accept the humerus, and creates the gleno-humeral joint.