NOUN (1)

1. imaginary people who live on the planet Mars;


ADJECTIVE (1)

1. of or relating to the planet Mars (or its fictional inhabitants);

The Collaborative International Dictionary of English v.0.48:

Martian \Mar"tian\, prop. a. [L. Martius.]
   Of or pertaining to Mars, the Roman god of war, or to the
   planet bearing his name; martial.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Martian \Mar"tian\, prop. n.
   An inhabitant of the planet Mars; -- fictional or
   hypothetical. --Du Maurier.
   [Webster 1913 Suppl.]

   Note: In science fiction, it has often been postulated that
         there are intelligent creatures living on Mars, but no
         strong evidence of any form of life on Mars has been
         observed up to the end of 1998.

Jargon File (4.4.4, 14 Aug 2003):

martian
 n.

   A packet sent on a TCP/IP network with a source address of the test
   loopback interface [127.0.0.1]. This means that it will come back
   labeled 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?" Compare Christmas tree packet,
   Godzillagram.