drop dead date

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++ˌdrop dead ˈdate noun [countable usually singular] American English informal  a date by which you must have completed something, because after this date it is no longer worth doing 〔必须完成某事，否则就不再值得去做的〕最后日期，最后期限，截止日期From Longman Business Dictionarydrop-dead datedrop-ˈdead date American English informal a date by which it is very important that you have done or completed something, because after this date it is no longer worth doing or completingThe original drop-dead date is June 23, but if all parties agree, there could be an extension. → date

ˌdrop dead ˈdate nounChineseSyllable  

Business have you by must because something, date a which after completed

drop dead date
ˌdrop dead ˈdate noun [countable usually singular] American English informal
a date by which you must have completed something, because after this date it is no longer worth doing