(historical) A small river in northeastern Italy which flowed into the Adriatic Sea marking the boundary between the Roman province of Gaul and the Roman heartland. Its crossing by Julius Caesar in 49 B.C.E. began a civil war.

Alternative letter-case form of rubicon (“a limit that when exceeded, or an action that when taken, cannot be reversed; especially in bezique and piquet: a score which, if not achieved by a losing player, increases the player's penalty”)

plural of rubicon

A limit that when surpassed cannot be returned from, or an action that when taken cannot be reversed.

(transitive, card games) Especially in bezique and piquet: to defeat a player who has not achieved the rubicon.

present participle of rubicon

simple past tense and past participle of rubicon

plural of Rubicon

(idiomatic) To make an irreversible decision or to take an action with consequences.

Third-person singular simple present indicative form of cross the Rubicon