Portal 2 what does ARG mean?

Answer 1

ARG stands for "alternate-reality game." They use it to refer to the canon of games that refer to Portal 2, like the recent Potato Sack Pack and the new DLC for Amnesia.

Here's a source: http://www.gamepro.com/article/news/214969/analysis-anatomy-of-an-alternate-reality-game/

Answer 2

An ARG or Alternate Reality Game is an interactive narrative that uses the real world as a game platform

Answer 3

alternate reality game

Answer 4

ARG means Alternate-Reality-Game Portal 2 just had one to promote it

Answer 5

It means Alternate-Reality Game

Answer 6

Alternate reality game.

 

If you don't know, this is an interactive "game" that typically breaks the fourth wall and has activities that interact with you outside of what is to be expected.

Ex: In Toki Tori, one of the potatoes must be gained by going to the Toki Tori website and downloading an "official" alternate level file to allow you to gain access to the potato in main game.