Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

concŭbĭus, a, um, adj. [concubo], of or belonging to lying in sleep, or to the time of sleep.

  1. I. As adj. only in the connection concubiā nocte (rarely: nocte concubiā, nocte in concubiā, noctu concubiā; v. the foll.), at the time of the first sleep, in the first sleep, Sisenn. ap. Non. p. 91, 22 (primi somni, Non.); Cic. Div. 1, 27, 57; Liv. 25, 9, 8; Tac. H. 3, 69; Just. 22, 8, 8: nocte concubiā, Tac. A. 1, 39: nocte in concubiā, Plin. 29, 6, 34, § 110: noctu concubiā, Enn. ap. Macr. S. 1, 4 (Ann. v. 170 Vahl.).
  2. II. As subst.: concŭbĭum, ii, n. (sc. tempus), that part of the night in which the first sleep falls upon men: si ante lucem occupias … concubium sit noctis prius quam, etc., Plaut. Trin. 4, 2, 44: concubium appellarunt, quod omnes fere tunc cubarent, Varr. L. L. 6, § 7 Müll.; cf. id. ib. 7, § 78 ib.; Censor. de Die Nat. 24; Macr. S. 1, 3 fin.; Serv. ad Verg. A. 2, 268.
    Hence,
    1. B. = concubitus, coition (perhaps only in the foll. exs.), Enn. ap. Non. p. 342, 23 (Trag. v. 241 Vahl.); Gell. 9, 10, 4.