Lewis & Short

imprĕcātĭo (inpr-), ōnis, f. [imprecor],

  1. I. an invoking of evil, imprecation (postAug.): exsecraris illum et caput sanctum tibi dira imprecatione defigis, curse, Sen. Ben. 6, 35, 1; id. Ep. 94, 52: imprecationes nefariae, Amm. 29, 1, 25: dira, Plin. 5, 8, 8, § 45.
  2. II. In late Lat., in a good sense, a prayer: pontificis, Hier. Ep. 130, n. 2.