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.

concŭbĭum, ii, n., v. concubius.

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.