Meaning of “ultimatum” - Learner’s Dictionary

ultimatum

noun [ C ] uk us /ˌʌltɪˈmeɪtəm/

a statement that you will do something that will affect someone badly if they do not do what you want:

The children were given an ultimatum - finish their work quietly or stay behind after class.

(Definition of “ultimatum” from the Cambridge Learner’s Dictionary © Cambridge University Press)