DECENNIAL Meaning of DECENNIAL in English [ dɪ'sɛnɪəl ]■ adjective lasting for or recurring every ten years.Derivatives~ly adverb OriginC17: from L. decennis (from decem 'ten' + annus 'year'), + -al . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004