[ roo-bi-kon ]

  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.

Idioms about Rubicon

  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.

Origin of Rubicon

First recorded in 1610–20

word story For Rubicon

In the late Roman Republic, the Rubicon was a border between Roman territory and one of Rome's provinces, Cisalpine Gaul. As the governor of a region that included this province, Julius Caesar had full command over his own army, but was forbidden to exercise this command within Roman territory. Caesar was a powerful, popular leader who had been victorious in many campaigns that the Senate did not authorize him to conduct. Tensions surrounding these unauthorized wars and fear of his popularity led the Senate to demand he give up his governorship and return to Rome to be tried for treason and war crimes. Caesar refused, and led his army into Rome. Before he marched his troops across the Rubicon, he still had a chance to change his mind and come back to Rome without initiating a civil war. But once the crossing was achieved, civil war was inevitable. Thus, in crossing the Rubicon, Caesar passed the point of no return.

Words Nearby Rubicon Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use Rubicon in a sentence

British Dictionary definitions for Rubicon


/ (ˈruːbɪkən) /

  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

  1. 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

  2. cross the Rubicon or pass the Rubicon to commit oneself irrevocably to some course of action

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Cultural definitions for Rubicon


[ (rooh-bi-kon) ]

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.

Notes for Rubicon

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

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Other Idioms and Phrases with Rubicon


see cross the rubicon.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.