1. To discredit, for example, to show that a witness is not believable—perhaps because the witness made statements that are inconsistent with their present testimony, or has a reputation for not being a truthful person.
2. The process of charging a public official, such as the U.S. president or a federal judge, with a crime or misconduct, which results in a trial to determine whether the official should be sanctioned or removed from office. Under the U.S. Constitution, impeachment is a political, not a criminal, proceeding. Officials are impeached—charged with misconduct—by the House of Representatives (U.S. Const. art. I, § 2, cl. 5) and are tried by the Senate. (U.S. Const. art. I, § 3, cl. 6.)