Lewis & Short

2. lustrum, i, n. [2. luo],

  1. I. a purificatory sacrifice, expiatory offering, lustration, made by the censors for the whole people once in five years, after completing the census, and in which a swine, a sheep, and a bull were offered (suovetaurilia): lustrum condere, to make the lustral sacrifice: lustrum condidit et taurum immolavit, Cic. de Or. 2, 66, 268: censu perfecto edixit, ut omnes cives Romani in campo primā luce adessent. Ibi exercitum omnem suovetaurilibus lustravit: idque conditum lustrum appellatum, quia is censendo finis factus est, Liv. 1, 44; 3, 24; cf. id. 35, 9; 38, 36; 42, 10. The census could also be taken without being followed by a lustrum, Liv. 3, 22, 1; 24, 43, 4: sub lustrum censeri, at the close of the census, when the lustrum should begin: sub lustrum censeri, germani negotiatoris est (because these were usually not in Rome, and were included in the census last of all), Cic. Att. 1, 18, 8.
    Being a religious ceremonial, the lustrum was sometimes omitted, when circumstances seemed to forbid it: census actus eo anno: lustrum propter Capitolium captum, consulem occisum, condi religiosum fuit, Liv. 3, 22, 1. Hence in part, doubtless, must be explained the small number of lustra actually celebrated; thus, A. U. C. 296: census perficitur, idque lustrum ab origine urbis decimum conditum ferunt, Liv. 3, 24, 10.
  2. II. Transf.
    1. A. A propitiatory offering: quinto die Delphis Apollini pro me exercitibusque et classibus lustra sacrificavi, Liv. 45, 41, 3.
    2. B. A period of five years, a lustrum (because every five years a lustrum was performed).
      1. 1. In gen.: cujus octavum trepidavit aetas Claudere lustrum, Hor. C. 2, 4, 24; Ov. Tr. 4, 10, 78; Mart. 10, 38, 9.
      2. 2. As the period of taxation, in reference to the imposition of duties, Varr, L. L. 6, 2, 11: hoc ipso lustro, Cic. Att. 6, 2, 5: superioris lustri reliqua, id. Fam. 2, 13, 3.
    3. C. In gen., a period of several years; of four years (of the Julian calendar), Ov. F. 3, 163; cf. Plin. 2, 47, 47, § 122: ingens lustrum, the grand lustrum, a hundred years, at the end of which the ludi saeculares were celebrated, Mart. 4, 1, 7.
    4. D. From the time of Domitian, the Capitoline games, recurring every fifth year, Suet. Dom. 4; Censor. de Die Nat. 18; cf. Stat. S. 4, 2, 60: certamine Jovis Capitolini lustro sexto, Inscr. Grut. 332, 3; called lustri certamen, Aur. Vict. Caes. 27, 7.
    5. E. Hectoris Lustra (not Lytra), title of a tragedy of Ennius; v. Trag. Rel. p. 28 sq. Rib.; Vahl. Enn. p. 113 sq.
  3. F. The term of a lease: priore lustro, Plin. Ep. 9, 37, 2.