1. [n]  imaginary people who live on the planet Mars
2. [adj]  of or relating to the planet Mars (or its fictional inhabitants)

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

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

Packets 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]