What is "acromioclavicular joint"

n. (context anatomy English) A joint at the top of the shoulder, the junction between the acromion and the clavicle.

The acromioclavicular joint, or AC joint, is a joint at the top of the shoulder. It is the junction between the acromion (part of the scapula that forms the highest point of the shoulder) and the clavicle. It is a plane synovial joint.