warning UK /ˈwɔːnɪŋ/US /ˈwoɹnɪŋ/noun 2exclamation 1forms 1phrases 2 noun2 •something said or written to let someone know about a danger or trouble aheadThe boss gave him a warning that he would be fired if he did not desist from his behaviour. •An instance of warning someone.Without much warning, a deep voice addressed the crowd, calling for a reverent silence as the Texans who died at the Alamo battle were named. — 2008 exclamation1 •Used to warn of danger in signs and notices. formswarnings Phrases with warning China's final warningA warning that carries no real consequences; an empty threat. four-minute warningA UK government public alert system in use during the Cold War to advise of an imminent nuclear attack.