|—n , pl -tums, -ta|
|1.||a final communication by a party, esp a government, setting forth conditions on which it insists, as during negotiations on some topic|
|2.||any final or peremptory demand, offer, or proposal|
|[C18: from New Latin, neuter of ultimatus|
A formal message delivered from one government to another threatening war if the receiving government fails to comply with conditions set forth in the message. For example, after the assassination of the Archduke Francis Ferdinand in 1914, the government of Austria sent an ultimatum to Serbia, which Austria held responsible for the assassination.