Sentence:  We are always passing the <WSD>Rubicon</WSD>, or being called upon to see somebody else pass it. Considering how often it has been passed, the Rubicon ought to be as well bridged as the Thames. [...] Looking back a few years, we find that that heaven-born minister, Pitt ["i.e.", w 
Meaning of the word marked with <WSD> tags:  A limit that when surpassed cannot be returned from, or an action that when taken cannot be reversed.