(1):

(n.) Hindrance; impediment; obstruction.

(2):

(n.) A calling to account; arraignment; especially, of a public officer for maladministration.

(3):

(n.) The act of impeaching, or the state of being impeached

(4):

(n.) A calling in question as to purity of motives, rectitude of conduct, credibility, etc.; accusation; reproach; as, an impeachment of motives.