Massive Crowd Simulation: "A Massive Crowd Simulation is a computer simulation of a crowd of agents. Agents are digital characters with a certain artificial intelligence. The individual agents can act on their own, they don't need to be pre-programmed or scripted, they respond on their environment without external control. They walk along a path, group together, hold distance, align with others, fight, patrol, get hurt, and can even die in their world." (Via Linkfilter.)