Lustration :: Lustration (n.) The act of lustrating or purifying.
Lustration :: Lustration (n.) A sacrifice, or ceremony, by which cities, fields, armies, or people, defiled by crimes, pestilence, or other cause of uncleanness, were purified..
Lustrum :: Lustrum (n.) A lustration or purification, especially the purification of the whole Roman people, which was made by the censors once in five years. Hence: A period of five years..