The Collaborative International Dictionary of English v.0.48:

Barbed \Barbed\, a.
   Furnished with a barb or barbs; as, a barbed arrow; barbed
   wire.
   [1913 Webster]

   Barbed wire, a wire, or a strand of twisted wires, armed
      with barbs or sharp points. It is used for fences.
      [1913 Webster]

WordNet (r) 3.0 (2006):

barbed wire
    n 1: strong wire with barbs at regular intervals used to prevent
         passage [syn: barbed wire, barbwire]