The Collaborative International Dictionary of English v.0.48:

Zareba \Za*re"ba\, n. (Mil.)
   An improvised stockade; especially, one made of thorn bushes,
   etc. [Written also zareeba, and zeriba.] [Egypt]
   [1913 Webster]

         "Ah," he moralizes, "what wonderful instinct on the
         part of this little creature to surround itself with a
         zareba like the troops after Osman Digma." --R.
                                                  Jefferies.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Zeriba \Ze*ri"ba\, n. (Mil.)
   Same as Zareba.
   [1913 Webster]