It doesn't mean a crime less than a felony, which is what it does mean in modern criminal law. It's a broad term that can include any offense or misdeed, statutory or otherwise.
The Convention came to its choice of words describing the grounds for impeachment after much deliberation, but the phrasing derived directly from the English practice. On June 2, 1787, the framers adopted a provision that the executive should “be removable on impeachment & conviction of mal-practice or neglect of duty.” The Committee of Detail reported as grounds “Treason (or) Bribery or Corruption.” And the Committee of Eleven reduced the phrase to “Treason, or bribery.” On September 8, Mason objected to this limitation, observing that the term did not encompass all the conduct that should be grounds for removal; he therefore proposed to add “or maladministration” following “bribery.” Upon Madison’s objection that “[s]o vague a term will be equivalent to a tenure during pleasure of the Senate,” Mason suggested “other high crimes & misdemeanors,” which was adopted without further recorded debate.
https://law.justia.com/constitution/us/article-2/50-impeachable-offenses.html
= new reply since forum marked as read
