Lewis & Short

2. occāsus, ūs, m. [occĭdo].

  1. I. A falling, going down (class.; cf. obitus).
    1. A. Lit., a going down, setting, of the heavenly bodies; esp. of the sun: ante occasum Maiae, Verg. G. 1, 225: ortus occasusque signorum, the rising and setting of the constellations, Quint. 1, 4, 4: solis, Caes. B. G. 1, 50; 2, 11; 3, 15; Liv. 9, 32.
      Absol.: praecipiti in occasum die, Tac. H. 3, 86.
    2. B. Transf., the quarter of the heavens in which the sun sets, sunset, the west: inter occasum solis et septentriones, Caes. B. G. 1, 1: ab ortu ad occasum, Cic. N. D. 2, 19, 49.
      Plur., Ov. M. 2, 190: ager Longus in occasum, Verg. A. 11, 317: de terrā occasus solis, Vulg. Zach. 8, 7.
    3. C. Trop., downfall, ruin, destruction, end, death: post obitum occasumque vestrum, Cic. Pis. 15, 34: occasus interitusque rei publicae, id. ib. 8, 18: id. Sull. 11, 33: Iliaci cineres et flamma extrema meorum, Testor, in occasu vestro, etc., Verg. A. 2, 432; cf. Trojae, id. ib. 1, 238: post L. Aelii nostri occasum, death, Cic. Ac. 1, 2, 8: odii, Quint. Decl. 9, 18.
  2. * II. For occasio, an occasion, opportunity, Enn. ap. Paul. ex Fest. p. 178 Müll. (Ann. v. 164; 171; 292 Vahl.).