Definition of the War Powers Act from the Oxford Advanced Learner's Dictionary

the War Powers Act

a 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 (= refusal to sign a law) by President Richard Nixon.