i Register
In some senses, octogenary is marked as obsolete. Watch for register when choosing this word.
adj
Of or related to the number 80, particularly
Of or related to the number 80, particularly
[…] he went to visit him, being then octogenary, and very decrepid with the gowt, but had his sight and understanding.
noun
Synonym of eightysomething: a person 80 to 89 years old.