<p><strong>Noun:</strong></p><ul><li>A river in northern Italy flowing east into the Adriatic; 15 miles (24 km) long; crossed by Julius Caesar when he marched against Rome in 49 B.C.</li><li>The act that commits someone to a particular course; point of no return; for example, "Publication serves as a Rubicon for authors, since they will be unable to edit their work afterward."</li></ul>