alternative reality game
n.— «ARGs, as they’re called, use real-world clues—from classified ads to answering-machine messages to URLs that show up in obscure places—to help players solve puzzles so intricate they might take groups to crack. Initial entry points are called “rabbit holes.” Some recent and current alternative reality games.» —“Alternate reality games” by Monty Phan Newsday (Long Island, N.Y.) May 25, 2005. (source: Double-Tongued Dictionary)