Lewis & Short

lăcus, ūs (gen. laci, Vulg. Dan. 6, 17; 24; id. Jer. 37, 15; Cassiod. Var. 11, 14; dat. and abl. plur. lacis, Anthol. Lat. 5, 71, 10: lacibus, Plin. 23, 1, 20, § 33; usually lacubus, Ov. M. 12, 278 al.), m. [root lak, to tear; Gr. λάκος, λακερός, λάκκος; Lat. lacer, lacinia, lacuna, lāma; cf. lacerna; originally any thing hollow, hence].

  1. I. A large vessel for liquids, a basin, tank, tub; esp. a vat into which the wine flowed from the press, Cato, R. R. 25; 67, 2; Col. 12, 18, 3: tu quoque devotos, Bacche, relinque lacus, Tib. 2, 3, 64: de lacubus proxima musta tuis, Ov. F. 4, 888; a tank of water, in which heated metal was cooled: alii stridentia tingunt Aera lacu, Verg. G. 4, 173: gelido ceu quondam lamina candens tincta lacu, stridit, Ov. M. 9, 170: ferrum, igne rubenslacubus demittit, id. ib. 12, 278.
    Hence,
    1. B. Transf.: oratio quasi de musto ac lacu fervida, i. e. still new, that has not done fermenting, Cic. Brut. 83, 288.
  2. II. A large body of water which rises and falls (opp. stagnum, a standing pool), a lake, pond: agri, aedificia, lacus, stagna, Cic. Agr. 3, 2, 7: exhalant lacus nebulam, Lucr. 5, 463: deae, quae illos Hennenses lacus lucosque incolitis, Cic. Verr. 2, 5, 72, § 188; cf. 2, 4, 48, § 107: Averni, Lucr. 6, 746; Cic. Tusc. 1, 16, 37: Albanus, id. Div. 1, 44, 100: Fucinus, Plin. 36, 15, 24, § 124: dicebar sicco vilior esse lacu, Prop. 2, 14 (3, 6), 12: ad spurcos lacus, Juv. 6, 603.
    Poet., of a river: deinde lacu fluvius se condidit alto Ima petens, Verg. A. 8, 66; cf. v. 74; of the Styx, id. ib. 6, 134; 238; 393.
  3. III. A large reservoir for water, a basin, tank, cistern (of which there were a great number in Rome), Front. 3; 78; Liv. 39, 44; Plin. 36, 15, 24, § 121: a furno redeuntes lacuque, Hor. S. 1, 4, 37.
    A place called Lacus: garruli et malevoli supra Lacum, at the pond (perh. Lacus Curtius or Lacus Juturnae), Plaut. Curc. 4, 1, 16.
    Prov.: siccus lacus, for something useless, Prop. 2, 11, 11 (3, 6, 12).
  4. IV.
        1. a. A hole in which lime is slacked, a lime-hole, Vitr. 7, 2, 2.
        2. b. One of the bins or receptacles for pulse in a granary: sed et lacubus distinguuntur granaria, ut separatim quaeque legumina ponantur, Col. 1, 6, 14.
        3. c. A den or cave for lions: labitur in lacum leonum, Prud. Cath. 4, 65; Vulg. Dan. 6, 7.
        4. d. The pit, the place of the dead (cf. II. fin. supra): salvasti me a descendentibus in lacum, Vulg. Psa. 29, 4.
  5. V. For lacunar, a panel in a ceiling (ante-class.): resultant aedesque lacusque, Lucil. ap. Serv. Verg. A. 1, 726.