A state of armed conflict between different countries or different groups within a country. ‘Japan declared war on Germany’ ‘the two countries were at war for the next eight years’ count noun ‘I fought in two wars’ 1.1 A state of competition or hostility between different people or groups. ‘she was at war with her parents’ count noun ‘a price war among tour operators’ 1.2 A sustained campaign against an undesirable situation or activity. ‘the authorities are waging war against smuggling’ count noun ‘a war on drugs’ verb [no object] Engage in a war. ‘small states warred against each another’ figurative ‘conflicting emotions warred within her’ Phrases go to war Declare, begin, or see active service in a war. ‘he joined the RAF before the country went to war’ ‘of the four brothers who went to war, only Thomas survived’ go to the wars archaic Serve as a soldier. ‘I did all I could to dissuade him from going to the wars’ be in the wars informal Be (or have been) injured. ‘Roebuck continues to be in the wars and suffered a broken jaw’ war clouds Used to refer to a threatening situation of instability in international relations. ‘the war clouds were looming’ war of attrition A prolonged period of conflict during which each side seeks to gradually wear down the other by a series of small-scale actions. war of words A prolonged, often acrimonious, debate. ‘the political war of words over tax’ war to end all wars A war, especially the First World War, regarded as making subsequent wars unnecessary. Origin Late Old English werre, from an Anglo-Norman French variant of Old French guerre, from a Germanic base shared by worse.