[A]fter a bill has passed both Houses of Congress, but “before it become[s] a Law,” it must be presented to the President. If he approves it, “he shall sign it, but if not he shall return it, with his Objections to that House in which it shall have originated, who shall enter the Objections at large on their Journal, and proceed to reconsider it.” Art. I, §7, cl. 2. His “return” of a bill, which is usually described as a “veto,” is subject to being overridden by a two-thirds vote in each House.
Clinton v. City of New York, 524 U.S. 417 (1998)