That's the term for a new technology developed by Harold Haas, professor of engineering at Edinburgh University. His plan? Turn ordinary LED light bulbs into broadband data transmission devices: Li-Fi.
Normal incandescent lights wouldn't work for this. The thermal inertia of their filaments would limit the date rate. But LED light bulbs can be turned on and off millions of times per second, making data rates in the 10's or 100's of Mbps possible. Here's a short video from CNNMoney about the idea.