Definition of nongenary in US English:

nongenary

noun

rare
  • (The celebration of) a nine hundredth anniversary.

Origin

1960s; earliest use found in The New Statesman. From post-classical Latin nongenarius containing nine hundred (5th–6th cent.; from nongeni nine hundred each (5th–6th cent.; shortened from nongenteni from classical Latin nōngentī nine hundred + -ēnī, suffix forming distributive adjectives: see nonagenarian) + -arius), after centenary.

Pronunciation

nongenary

/nɒnˈdʒiːn(ə)rɪ/