cross the Rubicon Definition

Rubicon
rubicon
noun

1. A boundary which, once crossed, commits someone crossing it to an irrevocable course of action.
2. cards.
In piquet: the winning of a game before one's opponent scores 100.

Idiom: cross the Rubicon (pass the Rubicon)

To take a decisive and irrevocable step.

Etymology: 17c: from the name of a stream in NE Italy that separated Julius Caesar's province of Cisalpine Gaul and Italy proper. By crossing the stream with his army in 49 bc Caesar effectively declared war on the Roman republic and began a civil war.