Definition of "acromioclavicular"

Frederick Matsen, the chairman of the department of orthopedics and sports medicine at the University of Washington, who has watched the hit that injured Bradford, said an injured acromioclavicular joint could be a bruise, a clavicle fracture, a mild separation or a severe separation.

2009 September 7, Thayer Evans, “Uncertainty About Oklahoma and Injury to Its Quarterback”, in New York Times‎