Jubilee (noun)

1. A special anniversary of an event, typically one marking 25 or 50 years.
2. A year of remission of sins and universal pardon proclaimed by the Pope for the Catholic Church, originally every 50 years, now every 25 years.
3. A time of celebration, especially a joyful celebration of a significant event.

Origin:

Middle english, from old french jubilé, from late latin jubilaeus, from latin jubilaeum, from jubilaeus joyful, from jubilare to exult, from jubilus exultation.

Examples:

1. The company was celebrating its 50th jubilee.
2. The Queen's diamond jubilee.
3. The Pope proclaimed a jubilee year of forgiveness.
4. The city was decorated for the jubilee.
5. They had a jubilee to celebrate the end of the war.