Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
millenary is a noun and adjective meaning "the 1000th anniversary (or the celebration of it)". It carries 5 recorded senses.
the 1000th anniversary (or the celebration of it)
a span of 1000 years
a sum or aggregate of one thousand (especially one thousand years)
of or relating to the doctrine of the millennium
relating to or consisting of 1000
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for millenary come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.