The crossword solution for the term 'CROSS THE RUBICON' is 'SWIM'. This phrase is derived from Julius Caesar's famous crossing of the Rubicon River in 49 BC, which marked the beginning of a civil war and the end of the Roman Republic. By crossing the Rubicon, Caesar was essentially committing treason against the Roman Senate, and his words 'alea iacta est' ('the die is cast') have become a symbol of taking a decisive action despite the risks.