eon

Short definition from Wiktionary

Noun

1. 1
   Eternity, the duration of the universe.
2. 2
   An immeasurably or indefinitely long period of time.
3. 3
   A long period of time.
4. 4
   A period of one billion (short scale, i.e. 1,000,000,000) years.
5. 5
   The longest geochronologic unit, being a period of hundreds of millions of years; subdivided into eras.
6. 6
   A spirit being emanating from the Godhead.

Proper noun

1. 1
   The Greek National Organisation of Youth, similar to the Hitler Youth. It was formed before WWII and disbanded in 1941.