The Council of Chalcedon was a significant event in the history of Christianity. It was a council held in Chalcedon in 451 AD to discuss and resolve certain theological controversies related to the nature of Christ. There are many synonyms that can be used to refer to the Council of Chalcedon, including the Fourth Ecumenical Council, the Council of Constantinople III, or the Council of 451. It is also sometimes referred to as the Council of Definition, as it provided a definition of the nature of Christ that is still used and debated by theologians today. Overall, the Council of Chalcedon remains an important milestone in Christian history.