Age

- noun.

Dictionary definition:
The length of time during which a being or thing has existed.

Video game definition:
The length of time during which a being or thing that is mostly likely a large barbaric man, a fire-breathing reptile, or a mind-enhancing puzzle have existed.

Usage:
Did you see that half-naked lady in the Dragon Age Origins trailer?
I can't believe Brain Age told me I had the mental health of a 30-year-old.

See also:
Age of Empires, Age of Mythology, Armored Core 2: Another Age, Warhammer Online: Age of Reckoning, Marvel vs. Capcom 2: New Age of Heroes, Age of Booty, Myst V: End of Ages.