War Powers Act:
US law passed in 1973 which allows Congress to limit the President’s use of military forces. It states that the President must tell Congress within 48 hours if he sends armed forces anywhere, and Congress must give approval for them to stay there for more than 90 days. The Act was passed in spite of a veto by President Richard Nixon
In My Own Words: A law passed in 1973 that states a war can go on for 90 days without the Congresses approval.
Use for definition http://www.oxfordlearnersdictionaries.com/us/definition/english/the-war-powers-act