Entry 1 sense Webster, 1913 Octogenarian /äkˌ-təj-ĭn-ĕr'-ē-ən/ · Oc·to·ge·na·ri·an · IPA /ˌɑktəd͡ʒɪˈnɛɹiən/ 01 n. A person eighty years, or more, of age. 1. A person eighty years, or more, of age.