Out of Game
Out of Game, or OOG, is a term used to describe any item, area, class, race, etc that has been removed from the game. Out of Game items (using the term loosely) generally cost more in the market, depending on their usefulness.
There exist some areas which are not always linked to the game, such as Midway of Despair. Items from these areas are not usually considered Out of Game, although effectively they are, until the area "opens" again and people can once more get these items.
Conversely, anything not Out of Game is In Game.