prop. n. (Anc. geog.) A small river which separated Italy from Cisalpine Gaul, the province alloted to
☞ By leading an army across this river, contrary to the prohibition of the civil government at Rome,
to pass the Rubicon or
cross the Rubicon signifies to take the decisive step by which one is committed to a hazardous enterprise from which there is no retreat. [ 1913 Webster ]