1 warn sb (of sth);warn sb (about sb/sth) to tell sb about sth unpleasant or dangerous that exists or might happen, so that he/she can avoid it 警告，提醒（某事可能要发生）: When I saw the car coming I tried to warn him, but it was too late. 我看到那辆车开过来就要警告他，但已经太迟了。The government is warning the public of possible terrorist attacks. 政府警告公众，恐怖分子可能发动攻击。He warned me about the danger of walking home alone at night. 他提醒我夜里独自步行回家有危险。

2 warn (sb) against doing sth;warn sb (not to do sth) to advise sb not to do sth 提醒，告诫（不要做某事）: The radio warned people against going out during the storm. 电台告诫人们暴风雨时不要出门。I warned you not to trust him. 我提醒过你不要相信他。