cross the Rubicon
To take a step you cannot undo.
Meaning adapted from Wiktionary, available under CC BY-SA 4.0.
“When she handed in her resignation, she crossed the Rubicon.”
“The company crossed the Rubicon the day it shut down the old system, because there was no longer anything to go back to.”
“Everyone in the room understood that signing the agreement would cross the Rubicon, committing them to a strategy that could be carried through or abandoned in ruin, but never quietly reversed.”
The Rubicon was an unremarkable stream in northern Italy, notable only for what it marked: the border between Caesar's province of Cisalpine Gaul and Italy proper. Roman law was blunt about it. A governor commanding an army could not bring that army across the line. To do so was to declare war on the Senate.
In January of 49 BC Caesar brought the Thirteenth Legion across anyway, and the Republic never recovered. Suetonius and Plutarch both linger on the pause at the bank — the moment when the thing was still undone — before the order was given.
To cross the Rubicon in English is to pass that same kind of line: the commitment after which the old options are gone, whatever happens next.
- 01
come home by weeping cross
To return in disappointment, or in a spirit of contrition.
- 02
cross my heart
A declaration that the speaker is telling the truth.
- 03
cross my heart and hope to die
Added to a promise or a statement to show how serious one was about being honest in what one said
- 04
cross of gold
A public policy which puts the interests of the rich ahead of those of the poor.
- 05
cross off
To strike out; to cross out; to draw a line through.
- 06
cross out
To strike out (something); to draw a line through (something).
- 07
cross paths
To be, by chance, in the same physical place at the same time, as a result of two completely separate journeys; to encounter or meet each other.
- 08
cross someone's palm
To pay for goods or a service.
One general, one river, and the end of the Republic.
- 01
the die is cast (idiom)
The decision is made and there is no going back.
What he said at the crossing.
- 02
veni, vidi, vici (idiom)
I came, I saw, I conquered — used of a job done fast and without difficulty.
Zela, 47 BC — the war report.
- 03
Caesar's wife must be above suspicion (idiom)
People in public positions must avoid even the appearance of wrongdoing, guilty or not.
The Bona Dea scandal, 62 BC.
- 04
beware the Ides of March (idiom)
A warning that a specific day, or a trusted circle, holds danger.
Spurinna's warning, 15 March 44 BC.
- 05
Et tu, Brute? (idiom)
Said when the person betraying you is the last one you expected.
Brutus, in the Senate.
- 06
sic semper tyrannis (idiom)
Thus always to tyrants — a slogan claiming that oppressors get what is coming to them.
What the assassins told themselves.
Last updated August 10, 2026