Lewis & Short

aequănĭmĭtas, ātis, f. [aequanimis] (rare for aequus animus).

  1. I. Before the class. per., favor, good-will (favor et propitius animus, Don. ad Ter. Ad. prol. 24): bonitas vestra atque aequanimitas, Ter. Phorm. prol. 34; id. Ad. prol. 24.
  2. II. In the post-Aug. per., calmness, patience, equanimity, Plin. 18, 12, 31, § 123: patien tia est malorum cum aequanimitate perlatio, Lact. 5, 22, 3.