From BrainChannels:
Mr. Csikszentmihalyi (pronounced chick-sent-me-high-ee) is chiefly renowned as the architect of the notion of flow in creativity; people enter a flow state when they are fully absorbed in activity during which they lose their sense of time and have feelings of great satisfaction. Mr. Csikszentmihalyi describes flow as “being completely involved in an activity for its own sake. The ego falls away. Time flies. Every action, movement, and thought follows inevitably from the previous one, like playing jazz. Your whole being is involved, and you’re using your skills to the utmost.”