Result from Foreign Dictionaries (2 entries found)
From The Collaborative International Dictionary of English v.0.48 [gcide]:
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.
[Webster 1913 Suppl.]
From WordNet (r) 3.0 (2006) [wn]:
diamond jubilee
n 1: an anniversary celebrating the passage of 60 years