ultimatum
n.a final demand that someone must accept to avoid a serious problem or punishment. It is a 'do this or else' message.
n.a final demand or statement of terms, the rejection of which will result in retaliation or a breakdown in relations. Often used in diplomatic, legal, or interpersonal negotiations.
“She gave him an ultimatum: arrive on time or leave.”
“The union issued an ultimatum to the management, threatening a full-scale strike if the safety demands were not met by midnight.”
“History is replete with diplomatic ultimatums that, while intended to force a peaceful concession, ultimately served as the formal precursors to declarations of war.”
Commonly follows the verbs 'issue', 'give', or 'deliver'.
“They warned MPs were "potentially being presented with a 'this or nothing' ultimatum on Friday".”
From Latin ultimatus (“late, last final”), from Latin ultimus (“extreme, last, furthest, farthest, final”).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.