means The wireless networking technology that lets your devices connect to the internet and each other over radio waves without cables.

from A genuinely funny case of a name that means nothing. 'Wi-Fi' was coined around 1999 by a branding firm, Interbrand, hired by the industry group promoting the IEEE 802.11 wireless standard — because '802.11b Direct Sequence' was never going to sell. People assume it stands for 'Wireless Fidelity,' echoing 'Hi-Fi' (high fidelity audio), but that phrase was invented AFTER the name, as a backronym to make the meaningless sound meaningful. The branders themselves have said it stands for nothing at all — it just sounded snappy next to 'Hi-Fi.'