Lustrum of wild beasts, plural lustra ( ), a den of vice. Lustrum A lustrum (, plural lustra) was a term for a five-year period in Ancient Rome. The lustration was originally a sacrifice for expiation and purification offered by one of the censors in the name of the Roman people at the close of the taking of the census. The sacrifice was often in the form of an animal sacrifice, known as a suovetaurilia. These censuses were taken at five-year intervals, thus a lustrum came to refer to the five-year inter-census period. ' (from ', ) is a lustration or
Lustrum 443 BC, and from this year down to 294 BC there had, according to Livy (X.47), only been 26 pairs of censors, and only 21 lustra, or general purifications, although if all had been regular, there would have been 30 pairs of censors and 30 lustra. Sometimes the census was not held at all, or at least not by the censors. The census might take place without the lustrum, and indeed two cases of this kind are recorded, in 459 and 214 BC. In these cases, the lustrum was not performed because of some great calamities that had befallen the