Source : Webster's Revised Unabridged Dictionary (1913)

Martian \Mar"tian\, a. [L. Martius.]
   Of or pertaining to Mars, the Roman god of war, or to the
   planet bearing his name; martial.

Martian \Mar"tian\, n.
   An inhabitant of the planet Mars. --Du Maurier.

Source : WordNet®

Martian
     adj : of or relating to the planet Mars (or its fictional
           inhabitants)
     n : imaginary people who live on the planet Mars

Source : Free On-Line Dictionary of Computing

Martian
     
        {Packet}s that turn up unexpectedly on the wrong {network}
        because of bogus {routing} entries.  Also a packet which has
        an altogether bogus (non-registered or ill-formed) {internet
        address}, such as the test loopback interface [127.0.0.1].
        Such a packet will come back labelled with a source address
        that is clearly not of this earth.  "The domain server is
        getting lots of packets from Mars.  Does that gateway have a
        martian filter?"
     
        [{Jargon File}]