1. cross the Rubicon - Verb
2. cross the Rubicon - Phrase
cross the Rubicon (third-person singular simple present crosses the Rubicon, present participle crossing the Rubicon, simple past and past participle crossed the Rubicon)
(idiomatic) To make an irreversible decision or to take an action with consequences.
He knew that by coming out to his family he would be crossing the Rubicon, but he could not live a lie anymore.