(noun) a joyful occasion for special festivities to mark some happy event. Synonyms: jubilation.
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Noun Definition 1
(noun) any joyous diversion. Synonyms: festivity.
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Noun Definition 2
(noun) the public performance of a sacrament or solemn ceremony with all appropriate ritual. Synonyms: solemnization, solemnisation. Example: "The celebration of marriage."