"rubicons" in the noun sense
1. Rubicon
the boundary in ancient times between Italy and Gaul Caesar's crossing it with his army in 49 BC was an act of war
2. Rubicon, point of no return
a line that when crossed permits of no return and typically results in irrevocable commitment
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License