jubilee
n//ˈd͡ʒubəl//jubelår, jubileum
(countable, Jewish, _, history) A special year of emancipation supposed to be observed every fifty years, when farming was temporarily stopped, certain houses and land which had been sold could be redeemed by the original owners or their relatives, and Hebrew slaves set free. [from late 14th c.]
A major anniversary of an event, particularly the fiftieth (50th) anniversary of a coronation or marriage. [from late 14th c.]