Real Dictionary

Western Church in American English
the Christian church in much of the western part of the Roman Empire
the Roman Catholic Church, sometimes with the Anglican Church, or, more broadly, the Christian churches of the West

Western Church in British English
noun: the part of Christendom that derives its liturgy, discipline, and traditions principally from the patriarchate of Rome, as contrasted with the part that derives these from the other ancient patriarchates, esp that of Constantinople