Rubicon(redirected from Rubicone)
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Rubicon(ro͞o`bĭkŏn), Lat. Rubico, small stream that flows into the Adriatic and in Roman times marked the boundary between Cisalpine Gaul and ancient Italy. In 49 B.C., after some hesitation, Julius Caesar crossed the Rubicon to march against Pompey in defiance of the senate's orders. He thus committed himself to conquer or to perish, and "to cross the Rubicon" now means to take an irrevocable step.
a river on the Italian peninsula, emptying into the Adriatic Sea, north of the city of Rimini. Until 42 B.C. it served as the border between Italy and the Roman province of Cisalpine Gaul. On Jan. 10, 49 B.C., Julius Caesar and his army illegally (as proconsul, he was entitled to head the army only outside Italy) crossed the Rubicon and invaded Italy, thus initiating civil war. Hence, the well-known expression “to cross the Rubicon,” meaning to make an irrevocable decision.