ˌWar on ˈTerrorism BrE AmE ( also ˌWar on ˈTerror ) noun [singular]
the name given to the actions and other measures taken by the US, Britain, and other countries to destroy international ↑ terrorist groups, especially al-Qaeda after the attacks on the World Trade Center and the Pentagon on September 11th, 2001. The actions taken include the wars in Afghanistan and Iraq.