Source : Webster's Revised Unabridged Dictionary (1913)

Io \I"o\, n.; pl. {Ios}. [L.; cf. Gr. "iw`.]
   An exclamation of joy or triumph; -- often interjectional.

Source : WordNet®

Io
     n 1: (Greek mythology) a maiden seduced by Zeus; when Hera was
          about to discover them together Zeus turned her into a
          white heifer
     2: the closest of Jupiter's moons; has active volcanoes

Source : Free On-Line Dictionary of Computing

IO
     
         Idiotic operator.
     
        (2003-05-15)

io
     
         The {country code} for British Indian Ocean
        territory.
     
        (1999-01-27)

I/O
     
        {Input/Output}