Ru·​bi·​con ˈrü-bi-ˌkän How to pronounce Rubicon (audio)
: a bounding or limiting line
especially : one that when crossed commits a person irrevocably

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In 49 B.C., Julius Caesar led his army to the banks of the Rubicon, a small river that marked the boundary between Italy and Gaul. Caesar knew Roman law forbade a general from leading his army out of the province to which he was assigned. By crossing the Rubicon, he would violate that law. "The die is cast," he said, wading in. That act of defiance sparked a three-year civil war that ultimately left Julius Caesar the undisputed ruler of the Roman world. It also inspired English speakers to adopt two popular sayings -crossing the Rubicon and the die is cast-centuries later. Rubicon has been used in English as the name of a significant figurative boundary since at least the early 1600s.

Examples of Rubicon in a Sentence

Recent Examples on the Web After less than a week, the fleet arrived at the aptly named Marina Rubicon, a popular launching point for Atlantic sailors. Thomas Curwen, Los Angeles Times, 26 June 2024 The estate in Rubicon Bay is available for the first time since it was acquired by Wellington Henderson and his wife Harriet Walker Henderson in the 1960s. David Caraccio, Sacramento Bee, 24 June 2024 And like all empires, this gang will experience a rise, a heyday, a Rubicon crossing and a fall. David Fear, Rolling Stone, 21 June 2024 This Rubicon of sorts — borrowing together — broke new ground, and arguably prevented the collapse of the E.U. into a deeper and longer recession. Matina Stevis-Gridneff, New York Times, 7 June 2024 There has been a shift toward hard-liners in both the Iranian and Israeli governments, and Israel’s strike on Iran’s consulate in Damascus crossed a Rubicon. Maha Yahya, Foreign Affairs, 24 Apr. 2024 Jeep Gladiator Rubicon High Top Concept is designed as a showcase for Jeep Performance Parts. Eric D. Lawrence, Detroit Free Press, 25 Mar. 2024 Whether literal or metaphoric, there’s a Rubicon that Owen has to cross. James Grebey, TIME, 17 May 2024 The Pro Football Hall of Fame passed an uncomfortable Rubicon in 2018 when the former Baltimore Ravens linebacker Ray Lewis spoke for more than 33 minutes at his induction ceremony. Ken Belson, New York Times, 3 Aug. 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'Rubicon.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


Latin Rubicon-, Rubico, river of northern Italy forming part of the boundary between Cisalpine Gaul and Italy whose crossing by Julius Caesar in 49 b.c. was regarded by the Senate as an act of war

First Known Use

1613, in the meaning defined above

Time Traveler
The first known use of Rubicon was in 1613


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Cite this Entry

“Rubicon.” Dictionary, Merriam-Webster, Accessed 21 Jul. 2024.

Geographical Definition


geographical name

Ru·​bi·​con ˈrü-bi-ˌkän How to pronounce Rubicon (audio)
river 15 miles (24 kilometers) long in north central Italy flowing east into the Adriatic Sea

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