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 or her opponent's - cross the Rubicon, pass the Rubicon ⇒
to commit oneself irrevocably to some course of action
WordReference Random House Unabridged Dictionary of American English © 2025
Ru•bi•con
(ro̅o̅′bi kon′),USA pronunciation n.
- Place Namesa river in N Italy flowing E into the Adriatic. 15 mi. (24 km) long: in crossing this ancient boundary between Cisalpine Gaul and Italy, to march against Pompey in 49b.c., Julius Caesar made a major military commitment.
- cross or pass the Rubicon, to take a decisive, irrevocable step:Our entry into the war made us cross the Rubicon and abandon isolationism forever.
Collins Concise English Dictionary © HarperCollins Publishers::