What is "ultimatums"

Ultimatum \Ul`ti*ma"tum\, n.; pl. E. Ultimatums, L. Ultimata. [NL. See Ultimate.] A final proposition, concession, or condition; especially, the final propositions, conditions, or terms, offered by either of the parties in a diplomatic negotiation; the most favorable terms a negotiator can offer, the rejection of which usually puts an end to the hesitation.

n. (plural of ultimatum English)