ˈləstrəm noun
( plural lus·trums -trəmz ; or lus·tra -trə)
Etymology: Latin; akin to Latin lucēre to shine — more at light
1.
a. : a purification of the whole Roman people made in ancient times after the census which was taken every five years
b. : the Roman census
2. : a period of five years : quinquennium
from 1797-1802 they shared a lustrum of sympathy and love — George Mallaby