the boundary in ancient times between Italy and Gaul; Caesar\\\'s crossing it with his army in 49 BC was an act of war
a line that when crossed permits of no return and typically results in irrevocable commitment
造句
用作名詞(n.)
That alarms many people, who fear that the border being crossed may be an inflationary Rubicon. 這拉響了很多人的警鐘，他們擔心正在突破通脹界限。
Although Wikipedia has prevented anonymous users from creating new articles for several years now, the new flagging system crosses a psychological Rubicon. 雖然維基百科已不允許匿名用戶創建新條目達數年之久，新的標記系統仍然超越心理界限。