ULTIMA'TUM, noun [Latin] 1..In diplomacy, the final propositions, conditions or terms offered as the basis of a treaty; the most favorable terms that a negotiator can offer, and the rejection of which usually puts an end to negotiation. It is sometimes used in the plural, ultimata. 2. Any final proposition or condition.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI