The Collaborative International Dictionary of English v.0.48:

No-man's land \No"-man's` land`\, No-man's-land
\No"-man's`-land`\
   1. (Naut.) A space amidships used to keep blocks, ropes,
      etc.; a space on a ship belonging to no one in particular
      to care for.
      [1913 Webster]

   2. An unoccupied area between opposing armies.
      [WordNet 1.5]

   3. Hence: (Fig.): An unclaimed space or time.
      [1913 Webster]

            That no-man's land of twilight.       --W. Black.
      [1913 Webster]