An emergency is an unexpected and difficult or dangerous situation, especially an accident, that happens suddenly and that requires quick action to deal with it. 突发事件; 紧急情况
noun [抽象名词]突发事件,紧急情况;急症病人,急诊病人;<美>(医院的)急诊室
The government had to take emergency action. 政府只得采取紧急措施。
adjective [原级]紧急情况下的;应急的
Yesterday, the centre's board held an emergency meeting. 昨天,中心的董事会召开了一次紧急会议。