From Longman Dictionary of Contemporary EnglishRubiconRu‧bi‧con /ˈruːbɪkən, -kɒn $ -kɑːn/ noun → cross the Rubicon
Examples from the Corpus
Rubicon• On the way to political union we are now crossing the Rubicon.Origin Rubicon (1600-1700) Latin Rubico river in northern Italy which Julius Caesar crossed in 49BC, setting off a civil war 