octogenarian
🇺🇸
/ˌɑːktədʒəˈneriən/
🇬🇧
/ˌɒktədʒəˈneəriən/
An 80 to 89-year-old person.
My grandmother, an octogenarian, is more active than many younger people I know.
我的祖母,一个八旬老人,比许多我认识的年轻更活跃。