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.

arcus, ūs, m. (the orthography, arquus (cf. arquatus), is freq. in MSS., like quum for cum, quur for cur, etc.; cf. Freund ad Cic. Mil. p. 31 sq. Thus Charis. p. 92 P. upon Cic. N. D. 3, 20, 51, reads arcuis; Prisc. p. 712 P. arci; and Non. p. 425, 5, upon Lucr. 6, 526, arqui; but the distinction which the latter gram. points out (arcus suspensus fornix appellatur; arquus non nisi qui in caelo apparet, quam Irim poëtae dixerunt) does not seem to be well founded.
Abl. plur. never found; acc. to the gram., Don. p. 1751, Diom. p. 285, Prisc. p. 779, Rhem. Palaem. p. 1371 P. al., it was arcubus; so Vulg. 2 Esdr. 4, 13; cf. Rudd. I. p. 104, n. 48.
Gen. sing. arqui, Lucr. 6, 526 Lachm., and Cic. N. D. 3, 20, 51 B. and K.
Dat. arcu, Sil. 4, 18.
Nom. plur. ARCVVS, Corp. Inscr. V. 85; Inscr. Henz. 5313: arci, Varr. ap. Non. p. 77, 12.
Acc. ARCOS, Corp. Inscr. II. 3420.
Fem., Enn. ap. Prisc. p. 712 P.; cf. id. 658 P.; and Serv. ad Verg. 6, 610, says that Catull. and others used it as fem.; v. Neue, Formenl. I. p. 679) [cf. Sanscr. arālas = bent, the bent arm, aratnis = Gr. ὠλένη; Lat. ulna; Germ. Elbogen; Engl. elbow. Curt.], prop., something bent; hence,

  1. I. A bow (syn. cornu).
    1. A. For shooting: intendit crinitus Apollo Arcum auratum, Enn. ap. Cic. Ac. 2, 28, 89 (Trag. v. 54 Müll.): arcus intentus in aliquem, Cic. Sest. 7: haec cernens arcum intendebat Apollo Desuper, Verg. A. 8, 704; 9, 665; so Vulg. Psa. 10, 3; 36, 14: arcum tendere, ib. 3 Reg. 22, 34; ib. 4 Reg. 9, 24: adductus, Verg. A. 5, 507: remissus, Hor. C. 3, 27, 67: arcum dirigere in aliquem, Pers. 3, 60: quom arcum et pharetram mi et sagittas sumpsero, Plaut. Trin. 3, 2, 98; so, arcum suscitare, Vulg. Hab. 3, 9 et saep.
    2. B. The rainbow (fully: pluvius arcus, v. infra, II.), Enn. ap. Prisc. p. 712 P. (Ann. v. 393 Vahl.): Tum color in nigris existit nubibus arqui, * Lucr. 6, 526 Lachm.: arcus ipse ex nubibus efficitur quodam modo coloratis, Cic. N. D. 3, 20, 51: ceu nubibus arcus Mille jacit varios adverso sole colores, Verg. A. 5, 88 Rib.; so Ov. M. 6, 63; 11, 632; 14, 838: pluvius describitur arcus, Hor. A. P. 18; Liv. 30, 2; 41, 21; Plin. 18, 35, 80, § 353; Sen. Q. N. 1, 5 and 6: arcum meum ponam in nubibus, Vulg. Gen. 9, 13 sqq. (in Vulg. Apoc. 4, 3; 10, 1, iris, q. v.) al.
    3. C. A bow or arch in building, a vault, arch, triumphal arch, etc.: efficiens humilem lapidum compagibus arcum, Ov. M. 3, 30; 3, 160; Juv. 3, 11; Suet. Ner. 25: marmoreus arcus, id. Claud. 1; so id. ib. 11; id. Dom. 13; cf. Plin. Pan. 59, 2 Schwarz.
  2. II. Transf.
    1. A. Poet. or in post-Aug. prose, any thing arched or curved like a bow; of the breaking of waves: niger arcus aquarum, Ov. M. 11, 568.
      Of the windings of a serpent: immensos saltu sinuatur in arcus, Ov. M. 3, 42.
      Of a curve in flight: dea se paribus per cælum sustulit alis Ingentemque fugā secuit sub nubibus arcum, Verg. A. 5, 658.
      Of the curving or bendings of a bay: sinus curvos falcatus in arcus, Ov. M. 11, 229 (cf.: inque sinus scindit sese unda reductos, Verg. A. 1, 161).
      Of a harbor: Portus ab Euroo fluctu curvatus in arcum, Verg. A. 3, 533.
      Of boughs of trees, Verg. G. 2, 26 et saep.
      Of the back of a chair, Tac. A. 15, 57.
    2. B. The mathematical arc, Sen. Q. N. 1, 10; Col. 5, 2, 9.
      Hence, of the five parallel circles of the globe which bound the zones (or perhaps rather, the zones themselves): via quinque per arcus, Ov. M. 2, 129.