adj. 1.  Of or relating to a 100-year period. 2.  Occurring once every 100 years. n. pl.   cen·ten·a·ries  1.  A 100-year period. 2.  A centennial. [Latin centēnārius, of a hundred, from centum, hundred; see  dek in the Appendix of Indo-European roots.]  | 
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