Definition of warn in US English:



  • 1reporting verb Inform someone in advance of an impending or possible danger, problem, or other unpleasant situation.

    with object ‘his father had warned him of what might happen’
    with direct speech ‘“He's going to humiliate you,” John warned’
    with clause ‘the union warned that its members were close to going on strike’
    • ‘Mr Sheard warns us of the dangers of Airedale and other local hospitals being incorporated into Bradford.’
    • ‘Bulky agricultural machinery which dominates country roads should be accompanied by advance warning vehicles, a coroner said.’
    • ‘We in the Newtown and Guillamene Swimming Club are constantly warning about the dangers but at the end of the day it's up to parents to ensure the safety of their children.’
    • ‘It has since emerged that she had been warned of the rumours at least two days before.’
    • ‘They're warning of a heightened possibility of an eruption after more than a thousand small earthquakes.’
    • ‘Was that old woman she met earlier telling the truth, and that she really was warning Alli of a possible danger that could befall her?’
    • ‘He was told that advance warning signs were put in place and that, if he could obtain permission from landowners, the council would remove some trees.’
    • ‘They become one-way routes, but they don't move, because people were not given the kind of advance warning they should get.’
    • ‘The report also warned of the dangers of failing to improve the lot of ordinary Iraqis.’
    • ‘The residents' acute fear of crime is itself a source of real danger, warns Budapest fire chief Peter Bende.’
    • ‘It was a habit left over from the old days when the king and his ministers were thus warned of danger.’
    • ‘Because of the possible dangers we are warning customers not to use them.’
    • ‘The conclusion also warns that I might possibly be frustrated if I don't have an outlet for my creative urges.’
    • ‘‘It was a nice sunny day, but unfortunately there were no signs, no flags warning us about the dangers,’ he said.’
    • ‘Hector said to his men warning them of the possible dangers of an ambush.’
    • ‘It also warns of the dangers of transferring patients when beds are not available.’
    • ‘The Bank of England is poised to warn of the dangers of a collapse in house prices.’
    • ‘Mary, on her way to Greenwich, was warned of the trap and rode pell-mell for Norfolk.’
    • ‘He also warned about the dangers of being divided by the scapegoating of refugees.’
    • ‘Parents also should be informed about the dangers and warning signs of inhalant abuse.’
    notify, alert, apprise, give notice, inform, tell, let someone know, make someone aware, give a warning to, give fair warning to, forewarn, put someone on guard, put someone on notice, remind
    View synonyms
    1. 1.1 Give someone forceful or cautionary advice about their actions or conduct.
      with object and infinitive ‘they warned people not to keep large amounts of cash in their homes’
      no object ‘they warned against false optimism’
      with object ‘friends warned her against the marriage’
      • ‘Police are warning farmers, horse owners and equestrian establishments to check security and be extra vigilant following a number of thefts in the North Wiltshire area.’
      • ‘Whatever the reason, Shuggy's behaviour eventually prompted a police caution, warning him that if he didn't calm down then he would be in serious trouble.’
      • ‘Police are warning people to be on their guard against credit card cheats after a Braintree woman had hers stolen and the thief tried to trick her into revealing her secret identity number.’
      • ‘Despite officers warning him about his conduct he continued to hurl insults and was arrested.’
      • ‘Police are warning motorists to expect severe problems with road closures, especially on Friday, and advising people to make other arrangements.’
      • ‘Police are warning residents not to confront a gang of brazen and aggressive thieves who have struck more than 50 times in Wiltshire, stealing power tools from vans.’
      • ‘More than 20 other people were sent letters from housing officials and police officers warning them that their behaviour could constitute a public nuisance.’
      • ‘Police officers are also warning elderly people to be on their guard tonight because Halloween can be rife with people committing distraction burglaries.’
      • ‘Police are warning drivers to remain cautious today after a winter storm dumped as much as 14 inches of snow on parts of eastern Virginia.’
      • ‘Police are warning elderly people to be on their guard after a Balham resident was duped out of £10, believing he was helping a neighbour.’
      • ‘Police warning Sinn Fein warned the government yesterday that a crisis was looming over the policing of Northern Ireland which may unravel the peace process.’
      • ‘The four were sent a letter from the council formally warning them about their conduct on January 20.’
      • ‘Police are warning troublemakers that their behaviour will not be tolerated following another weekend of assaults and vandalism.’
      • ‘Police are warning the public to be cautious when opening their door to strangers.’
      • ‘Well, we have for a long time provided early warning advice on the launch of ballistic missiles.’
      • ‘Now police are warning anyone who used the machine over the Easter weekend, including the bank holiday Monday, to check their bank accounts in case they too have become victims of the scam.’
      • ‘A huge pop concert for girl guides, a demonstration, and two major sporting events all take place on Saturday, and police are warning drivers to stay clear.’
      • ‘Police are warning farmers to secure valuable machinery and to mark it for identification, as well as maintaining serial number records.’
      • ‘Then suddenly and without warning the police moved in on horseback and foot, wrestling random fans to the floor and using their batons with sickening accuracy.’
      • ‘Police are warning people to make sure their houses are secure even when they are in them following a spate of ‘creeper’ burglaries.’
      advise, exhort, urge, counsel, caution
      View synonyms

Phrasal Verbs

  • warn someone off

    • 1Tell someone forcefully or threateningly to go away or stay.

      1. 1.1Advise someone forcefully against (a particular thing or course of action)
        ‘he has been warned off booze’
        • ‘I swore and cursed at him for a couple of minutes and he warned me off.’
        • ‘The couple decided to try for a baby without seeking specialist advice in case they were warned off due to the risks involved.’
        • ‘‘The police went to see the guy, warned them off and it stopped,’ he said.’
        • ‘When he was warned off writing the book by Naipaul's second wife, it just made him all the more determined.’
        • ‘That's why we weren't warned off the attack sooner.’
        • ‘I keep waiting for him to warn me off, to use his own crippling accident and this video to scare me straight.’
        • ‘While many shunned the Ayrshire stockbroker during his period of exile from the tracks - he was warned off for ten years for his part in scandal.’
        • ‘If they try to pester you into buying their cover, turn it down flat and threaten to walk out - this should warn them off!’
        • ‘Mark pointed at one on one of the stands and the smiley woman helping us warned him off.’
        • ‘Mealtimes are loaded with messages, subliminal and explicit, to warn you off or turn you on.’
        • ‘Osileani pulled his weapon in front of the crone's haggard faces, warning them off with a cautious step.’
        • ‘I had asked him what he wanted, because I hadn't met such nice boys before, and the last time I did meet someone I liked, Kip had warned him off.’
        • ‘Has the Home Office been on the blower to warn you off?’
        • ‘The rebels in Shanghai had been warned off interfering with the secretariat of the East China Bureau on the grounds that it was an organ of the Central Committee.’
        • ‘Police reportedly found evidence of sabotage, but were happy to call the crash an accident when, it is said, they were warned off looking too closely.’
        • ‘Medication is contra-indicated and he has been warned off excessive alcohol usage.’
        • ‘Just as he is about to get to the bottom of the affair, he is warned off by the American ambassador in Saigon.’
        • ‘Now when John Main began has explorations into meditation he was warned off that path by his own order, was he not?’
        • ‘When the media arrived, two men came out and tried to warn them off.’
        • ‘When I came in behind him in a thermal in the start circle he deliberately turned back and into me to intimidate me and warn me off.’


Old English war(e)nian, wearnian, from a West Germanic base meaning ‘be cautious’; compare with ware.