Lustrum
Pronunciation : Lus"trum, n.; pl. E. Lustrums
Part of Speech : L.
Etymology : [L. Cf. 2d & 3d Luster.]
Definition : Defn: 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.
Lustra.
Source : Webster's Unabridged Dictionary, 1913