quindecennial

[ kwin-di-sen-ee-uh l ]
/ ˌkwɪn dɪˈsɛn i əl /

adjective

of or relating to a period of 15 years or the 15th occurrence of a series, as an anniversary.

noun

a 15th anniversary.

Origin of quindecennial

< Latin quīndec(im) fifteen + -ennial (as in decennial)
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British Dictionary definitions for quindecennial

quindecennial

/ (ˌkwɪndɪˈsɛnɪəl) /

adjective

occurring once every 15 years or over a period of 15 years

noun

a 15th anniversary

Word Origin for quindecennial

C20: from Latin quindecim fifteen + annus year, on the model of biennial
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012