ul·ti·ma·tum/ˏʌltə`metəm; ˌʌltɪˈmeɪtəm/ n [C] a warning that if someone does not do something, you will do something that will have a bad effect on them 最后通牒: issue/give an ultimatum The government issued an ultimatum to the rebels to surrender. 政府向叛乱分子发出最后通牒，要他们投降。