D defs.my
Entry 1 sense Webster, 1913

Lustrum

· Lus·trum · IPA /ˈlʌstɹəm/
01 n. A lustration or purification, especially the purification of the whole Roman people, which was made by the censors once in five years.
pl. Lustrums, Lustra ((#))
  1. 1.
    A lustration or purification, especially the purification of the whole Roman people, which was made by the censors once in five years.