The power of one branch of government to prohibit a certain action by another; for example, the chief executive's right to refuse to sign a legislature-passed bill into law. 2 v. The act of refusing or canceling the act of another or the passage of a law. vexatious litigation pocket veto. As to a chief executive of a governmental body, such as the President of the United States, the failure to approve a proposed legislative act, thereby resulting in the proposed law not being passed, and ther...