OCTOGENARIAN Meaning of OCTOGENARIAN in English [ ˌɒktə(ʊ)dʒɪ'nɛ:rɪən ]■ noun a person who is between 80 and 89 years old.OriginC19: from L. octogenarius (based on octoginta 'eighty') + -an . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004