Also found in: Dictionary, Thesaurus, Legal, Acronyms, Idioms, Encyclopedia, Wikipedia. shoulder. the area around the glenohumeral joint, the large ball-and-socket joint where the humerus joins the scapula. The smooth, rounded head of the humerus rests against the socket in the scapula. The joint is covered by a tough, flexible protective capsule and is heavily reinforced by ligaments that stretch across the joint.