'Nonagenarian' definitions:

Definition of 'nonagenarian'

(from WordNet)
adjective
Being from 90 to 99 years old; "the nonagenarian inhabitants of the nursing home"
noun
Someone whose age is in the nineties

Definition of 'Nonagenarian'

From: GCIDE
  • Nonagenarian \Non`a*ge*na"ri*an\, n. [L. nonagenarius containing, or consisting of, ninety, fr. nonageni ninety each; akin to novem nine.] A person ninety years old. [1913 Webster]

Synonyms of 'nonagenarian'

From: Moby Thesaurus