What is the meaning of Lustrum?

A lustration: a ceremonial purification of the people of Rome performed every five years after the census.

Synonym of quinquennium: Any 5-year period.

bog, morass, place where boars and swine wallow

den or lair of wild beasts; wood, forest

(a place of) debauchery

a purificatory sacrifice (expiatory offering) or lustration performed every five years by the censor

a period of five years

Source: wiktionary.org