SEPTUAGENARIAN Meaning of SEPTUAGENARIAN in English [ ˌsɛptjʊədʒɪ'nɛ:rɪən ]■ noun a person who is between 70 and 79 years old.OriginC18: from L. septuagenarius (based on septuaginta 'seventy') + -an . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004