The definition of an ultimatum is a demand which, if not met, will end a relationship or otherwise result in some serious consequence.(noun)
When a woman says to her boyfriend "marry me or I am leaving you," this is an example of an ultimatum.
See ultimatum in Webster's New World College Dictionary
Origin: ModL < LL, neut. of ultimatus: see ultimate
See ultimatum in American Heritage Dictionary 4
noun pl. ul·ti·ma·tums or ul·ti·ma·ta (-tə)
Origin: New Latin
Origin: , from neuter of Latin ultimātus, last; see ultimate.
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