Pl. lustra, lustrums, erron. lustras. [L. lūstrum; usu. believed to be f. root of luĕre to wash (cogn. w. lavāre LAVE v.).]
1. Rom. Antiq. A purificatory sacrifice made by the censors for the people once in five years, after the census had been taken. Hence, the census itself.
1598. Grenewey, Tacitus’ Ann., XI. viii. (1622), 150. He [Claudius] … appointed a view to be taken of the city which is called Lustrum, and the number of the citizens to be inrolled.
[1780. Ann. Reg., Chron., 224/2. We hear from Rome that they had a lustrum (or a numbering of the people) there on the 24th of June, when it appeared there were in that city 155,184 inhabitants.]
2. A period of five years.
In Latin sometimes used for a period of four years.
1590. L. Lloyd, Consent of Time, To Rdr. a 3. Can any true accompt of time be made … by the censure of Lustrum, which the Grecians call Penteterides.
1601. Holland, Pliny, I. 24. The Lustrum or computation of the fiue yeares beginneth at the leap yere, when the Dogstar doth arise.
1666. J. Smith, Old Age, 264. Prolonging them … to so many years or Lustras.
1680. T. Flatman, Heraclitus Ridens, No. 71 (1713), II. 189. Till two short Lustra o’re your Sacred Head shall flow.
1742. Young, Nt. Th., II. 173. We push time from us, and we wish him back; Lavish of lustrums, and yet fond of life.
a. 1849. Poe, Morella. Thus passed away two lustra of her life.
1901. M. T. F. McCarthy, Five Yrs. Irel., xxiv. 343. There were, during the lustrum under review, 1077 men in Ireland who had been called to the Bar.
3. U.S. In college use.
1850. W. R. Williams, Relig. Progr., i. (1854), 36. It is the book not of an academic lustrum only, nor of a lifetime, but of generations.
1860. C. Durfee, Hist. Williams Coll., 290. A proposition was then submitted to the Alumni … that the classes in lustrums, or divisions of fours, engage to contribute two hundred and fifty dollars each.
