razor wire
From Longman Dictionary of Contemporary Englishrazor wireˈrazor ˌwire noun [uncountable] DCBstrong wire with sharp edges, used to keep people out of a building, area of land etcExamples from the Corpusrazor wire• The inmates are held in a compound encircled by razor wire.• They gazed into my torch beam like cons caught in razor wire.• There were fences with spirals of razor wire on top.• The following day 20 protesters climbed back over the razor wire.• The gear is protected by a cyclone fence topped with razor wire.• The high grey wall has a lip trimmed with razor wire.