of or relating to a period of 15 years or the 15th occurrence of a series, as an anniversary.
a 15th anniversary.
Origin of quindecennial
< Latin quīndec(im) fifteen + -ennial (as in decennial)
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occurring once every 15 years or over a period of 15 years
a 15th anniversary
Word Origin for quindecennial
C20: from Latin quindecim fifteen + annus year, on the model of biennial
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