Lewis & Short

dīrĭtas, ātis, f. [dirus] (rare but class.), lit. fearfulness, viz.,

  1. I. Of fate, fatal mischief, misfortune: si qua invecta diritas casu foret, Cic. Poët. Tusc. 3, 14: totius diei, Suet. Ner. 8; cf. ominis, Gell. 4, 9, 10.
  2. II. Of character, fierceness, cruelty: omni diritate atque immanitate teterrimus, Cic. Vatin. 3 fin.: quanta in altero diritas, in altero comitas! id. de Sen. 18 fin.: morum (Tiberii), Suet. Tib. 21.