A presidential veto is a constitutional power that allows a president to reject legislation passed by the legislature. This mechanism serves as a check on legislative authority, ensuring that the president can prevent the enactment of laws perceived as harmful or contrary to the public interest. When a president issues a veto, the legislature can respond by attempting to override it, typically requiring a supermajority vote. This process maintains a balance of power between the executive and legislative branches, fostering dialogue and negotiation in the law-making process while ensuring accountability to the electorate.