WiFi

Wireless Fidelity: WiFi may be considered an acronym specifically for (Wi)reless (Fi)delity (IEEE 802.11b wireless networking). However, WiFi is more of a catch phrase than a real acronym since it has come to refer to an umbrella of wireless networking technologies. WiFi is the name commonly given to wireless networking technology that uses radio waves to provide wireless high-speed Internet and network connections.

According to author Cory Doctorow WiFi isn't short for "Wireless Fidelity", it doesn't mean anything.

The term Wi-Fi is in fact a registered trademark owned by Wi-Fi Alliance. The Wi-Fi Alliance organisation specifically defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards." A pioneer of the Wi-Fi Alliance is quoted as saying "Wi-Fi doesn't stand for anything. It is not an acronym. There is no meaning."