To accuse; to charge a liability upon; to sue. To dispute, disparage, deny, or contradict; as in to impeach a judgment or decree, or impeach a witness; or as used in the rule that a jury cannot impeach its verdict. To proceed against a public officer for crime or misfeasance, before a proper court, by the presentation of a written accusation called ARTICLES OF IMPEACHMENT.

In the law of evidence, the testimony of a witness is impeached by earlier statements that the witness has made if they are inconsistent with the statements to which the witness testifies.