vigintennialadj.
/vʌɪdʒɪnˈtɛnɪəl/ rare.
Occurring once in twenty years.
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the world > time > period > year > [adjective] > occurring every specific number of years
quinquennal1532
quinquennial1601
five-yearly1619
centenary1620
septennial1640
triannual1640
triennial1642
septennary1644
sexennial1646
trieterical1646
novennial1656
octennial1656
trieteric1656
quinquennalian1692
quadrenniala1700
biennial1750
sexennary1753
lustral1781
centennial1797
quaternal1813
sextennial1814
septendecennial1834
septemdecenary1843
undecennarya1847
bicentenary1862
bicentennial1883
quadricentennial1889
trigintennial1894
twelve-yearly1906
vigintennial1921
1921 Glasgow Herald 29 Jan. 13/3 Their [sc. the planets'] vigintennial conjunction is due a few months hence.
This entry has not yet been fully updated (first published 1933; most recently modified version published online March 2018).
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adj.1921