octogenarian

nouns

someone whose age is in the eighties
octogenarian
is a type of (narrower)
an elderly person
golden ager, old person, oldster, senior citizen

adjectives

being from 80 to 89 years old
octogenarian
is similar to
(used especially of persons) having lived for a relatively long time or attained a specific age
"his mother is very old"; "a ripe old age"; "how old are you?"
old