Lewis & Short

cāsŭālis, e, adj. [casus].

  1. I. Casual, fortuitous (post-class. and very rare): condicio, depending upon chance, Cod. Just. 6, 51, 1, § 7.
    Adv.: cāsŭālĭter, accidentally, Sid. Ep. 9, 11; Fulg. Myth. 1, 5.
  2. II. In gram., relating to or declined with cases: Casuale, ut ab equo: equum, Varr. L. L. 8, § 52, p. 116 Bip.; cf. id. ib. 10, § 18, p. 164 Bip.: formae, Prisc. p. 672 P. al.