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 history shows the current battle for the strait is just the latest iteration of a centuries-old fight to control the critical trade route—and why it has become a Rubicon for American presidents.

From The Wall Street Journal • Mar. 22, 2026

They respect the skills of the elite Russian drone units they said were called Rubicon and Day of Judgement.

From BBC • Feb. 24, 2026

Investors are running away from the dollar into gold and other assets, but the real Rubicon for markets is the long bond, according to Bank of America chief investment strategist.

From MarketWatch • Jan. 29, 2026

The high school students only realised they had brushed up on the wrong Roman ruler when they crossed the Rubicon to sit down for their final-year exams.

From Barron's • Oct. 29, 2025

He never suspected that in so doing, he was crossing his Rubicon.

From "Into the Wild" by Jon Krakauer