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[roo-bi-kon] /ˈru bɪˌkɒn/
a river in N Italy flowing E into the Adriatic. 15 miles (24 km) long: in crossing this ancient boundary between Cisalpine Gaul and Italy, to march against Pompey in 49 b.c., Julius Caesar made a major military commitment.
cross / pass the Rubicon, to take a decisive, irrevocable step:
Our entry into the war made us cross the Rubicon and abandon isolationism forever. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for Rubicon
Contemporary Examples
Historical Examples
  • He crossed the Rubicon of a door-mat and stood in the unlighted hall.

    The Spenders Harry Leon Wilson
  • Caesar led his army into Italy to the borders of the Rubicon.

    Introductory American History Henry Eldridge Bourne
  • It had already crossed the Rubicon and passed over to the Entente.

    England and Germany Emile Joseph Dillon
  • I saw that my fair sweetheart had crossed the Rubicon; the day was won.

    The Memoires of Casanova, Complete Jacques Casanova de Seingalt
  • The antecedent in this instance is not Rubicon, but the entire clause.

    The Verbalist Thomas Embly Osmun, (AKA Alfred Ayres)
British Dictionary definitions for Rubicon


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
(sometimes not capital) a point of no return
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
cross the Rubicon, 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
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Word Origin and History for Rubicon

in phrase to cross (or pass) the Rubicon "take a decisive step," 1620s, a reference to a small stream to the Adriatic on the coast of northern Italy which in ancient times formed part of the southern boundary of Cisalpine Gaul; crossed by Caesar Jan. 10, 49 B.C.E., when he left his province to attack Pompey. The name is from Latin rubicundus "ruddy," in reference to the color of the soil on its banks.

Online Etymology Dictionary, © 2010 Douglas Harper
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Rubicon in Culture
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.

Note: “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 Company.
Published by Houghton Mifflin Company. All rights reserved.
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Idioms and Phrases with Rubicon


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