Source : WordNet®

WiFi
     n : a local area network that uses high frequency radio signals
         to transmit and receive data over distances of a few
         hundred feet; uses ethernet protocol [syn: {wireless
         local area network}, {WLAN}, {wireless fidelity}]

Source : Free On-Line Dictionary of Computing

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.
     
        (2003-09-02)