An abbreviation for Darcology, a high density living structure in the game Sim City. Darcos have dark, twisting tunnels that lead nowhere, and a mysterious sub human race reputedly inhabits the air ducts. The residents spend most of their time writing code. drinking coffee. A haven and monastery for geeks, nerds and perl monks, because inside, it's night-time all the time. Aberdeen Inverness, a dorm at UC Riverside is a good example of an real life Darco.