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
双语例句
用作名词 (n.)
That alarms many people, who fear that the border being crossed may be an inflationary Rubicon. 这拉响了很多人的警钟，他们担心正在突破通胀界限。
Although Wikipedia has prevented anonymous users from creating new articles for several years now, the new flagging system crosses a psychological Rubicon. 虽然维基百科已不允许匿名用户创建新条目达数年之久，新的标记系统仍然超越心理界限。
