Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Diamond anniversary \Diamond anniversary\, Diamond jubilee \Diamond jubilee\, etc. an anniversary celebrated upon the completion of sixty, or, according to some, seventy-five, years from the beginning of the event commemorated.
WordNet
n. an anniversary celebrating the passage of 60 years
Wikipedia
A diamond jubilee is a celebration held to mark a 60th or 75th anniversary.
Diamond Jubilee (1897 – 10 July 1923) was a British-bred and British-trained Thoroughbred race horse and sire. In a career which lasted from June 1899 until October 1901 he ran sixteen times and won six races.
He showed modest form as a two-year-old in 1899 but improved to be the leading colt of his generation in 1900 when he won the British Triple Crown. His other wins included the Eclipse Stakes, then one of the most valuable horse races in the world. He was retired to stud at the end of the 1901 season and was later exported to Argentina.
Diamond Jubilee was noted throughout his life for his unpredictable and sometimes violent temperament.
Usage examples of "diamond jubilee".
It's a grand ball to celebrate Her Majesty's Diamond Jubilee, and I've never seen such a throng.
Queen Victorias Diamond Jubilee was celebrated and the college on top of the hill in Moseley was illuminated with coloured lights.
Here came Queen Victoria, first small and then enormous in a royal carriage, part of a silent procession celebrating Her Majesty's diamond jubilee.
Ma claims she celebrated her twenty-first the year of Victoria's Diamond Jubilee, but I don't know about that.
The events of that year of Her Majesty's Diamond Jubilee had disabused me of my basic misconceptions on the subject—.