octogenarian

UK: English: /ˌɒktəʊdʒɪˈnɛərɪən/, Dutch: /ɒkˈtɒdʒɪnərɪ/

US: /ˌɑktədʒəˈnɛriən/

US: (ok′tə jə nâr′ē ən)

WordReference Random House Learner's Dictionary of American English © 2025

oc•to•ge•nar•i•an /ˌɑktədʒəˈnɛriən/  n. [countable]

1. one between 80 and 90 years old.

WordReference Random House Unabridged Dictionary of American English © 2025

oc•to•ge•nar•i•an  (ok′tə jə nâr′ē ən), adj. Also, oc•tog•e•nar•y 

(ok toj′ə ner′ē). 
1. of the age of 80 years.
2. between 80 and 90 years old.

n. 

3. a person who is between 80 and 90 years old.

• Latin octōgēnāri(us) comprising eighty, eighty years old (equivalent. to octōgēn(ī) eighty each + -ārius -ary) + -an
• 1805–15

oc′to•ge•nar′i•an•ism, n. 

Collins Concise English Dictionary © HarperCollins Publishers::

octogenarian / ˌɒktəʊdʒɪˈnɛərɪən/, (less commonly)octogenary / ɒkˈtɒdʒɪnərɪ/ noun ( -narians, -naries)

1. a person who is from 80 to 89 years old

adjective

1. of or relating to an octogenarian

Etymology: 19th Century: from Latin octōgēnārius containing eighty, from octōgēnī eighty each