Lewis & Short

ingrātĭtūdo, ĭnis, f. [ingratus].

  1. I. Unthankfulness, ingratitude (late Lat. for animus ingratus), Firm. 5, 1 med.; Cassiod. Var. 5, 8.
  2. II. Displeasure, Cassiod. Var. 1, 30.