Rubicon

American  

[roo-bi-kon] / ˈru bɪˌkɒn /

noun

1. a river in northern Italy flowing east into the Adriatic. 15 miles (24 km) long: crossed by Julius Caesar when he marched against Rome in 49 b.c.

2. Sometimes rubicon the act that commits someone to a particular course; point of no return.

   Publication serves as a Rubicon for authors, since they will be unable to edit their work afterward.

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idioms

1. cross / pass the Rubicon, to take a decisive, irrevocable step.

   Our entry into the war made us cross the Rubicon and abandon isolationism forever.

Rubicon British  

/ ˈruːbɪkən /

noun

1. a stream in N Italy: in ancient times the boundary between Italy and Cisalpine Gaul. By leading his army across it and marching on Rome in 49 _bc , Julius Caesar broke the law that a general might not lead an army out of the province to which he was posted and so committed himself to civil war with the senatorial party

2. (sometimes not capital) a point of no return

3. a penalty in piquet by which the score of a player who fails to reach 100 points in six hands is added to his opponent's

4. to commit oneself irrevocably to some course of action

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Rubicon Cultural  

1. A river in northern Italy that Julius Caesar crossed with his army, in violation of the orders of the leaders in Rome, who feared his power. A civil war followed, in which Caesar emerged as ruler of Rome. Caesar is supposed to have said, “The die is cast” (referring to a roll of dice), as he crossed the river.

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Rubicon More Idioms  

1. see cross the rubicon.

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Discover More

“Crossing the Rubicon” is a general expression for taking a dangerous, decisive, and irreversible step.

Etymology

Origin of Rubicon

First recorded in 1610–20

Example Sentences

"But it was a little bit more than that. It was forging through a Rubicon that was never forged through before. It was debated in the Houses of Parliament," he said.

From BBC • Apr. 10, 2026

Schneiderman said it is "highly unlikely that the US will choose to use nuclear weapons against Iran. It is the ultimate Rubicon to cross."

From Barron's • Apr. 7, 2026

More recently, Hormuz and the Persian Gulf have been a Rubicon for American presidents, sometimes defining their foreign policy and taste for exercising military power.

From The Wall Street Journal • Mar. 21, 2026

“The world’s most important commodity has crossed the Rubicon, and the ripple effects are only beginning to spread,” Stephen Innes, managing partner at SPI Asset Management, said in a Sunday note.

From MarketWatch • Mar. 8, 2026

Julius Caesar’s army wouldn’t have left such a mess after crossing the Rubicon.

From "The Wednesday Wars" by Gary D. Schmidt