formal meeting of representatives of different countries, states, organizations, etc.
In politics, a congress is a political meeting of leaders or representatives of groups of people. Until the 19th century it was usually a meeting of kings or their representatives, for example the Congress of Vienna. Today it often means the main legislature that makes the laws for a state. The word congress can also mean a meeting of associations, as in the Trades Union Congress (TUC), of the United Kingdom, a meeting of trade unions.