wi-fi
Either of two different incompatible radio-based LAN protocols, namely 802.11b (which speaks DSSS at 2.4GHz) and 802.11a (which speaks OFDM at 5GHz).
The term was invented by the marketing departments of wi-fi equipment manufacturers. It is, notionally, short for "wireless fidelity", on the analogy of hi-fi for "high fidelity" audio.