How does the term "Waterloo" function in a figurative sense in modern language?

The term "Waterloo" functions in a figurative sense as a reference to a decisive defeat because it originates from the historic Battle of Waterloo in 1815, where Napoleon Bonaparte faced a significant and final defeat. This event marked the end of his military campaigns and reign, and as such, the term has evolved in modern language to symbolize any overwhelming or catastrophic loss. When someone describes a situation as their "Waterloo," they are alluding to a moment of significant failure where their efforts were conclusively thwarted. This figurative use captures the essence of the historical event, encapsulating the idea of encountering a turning point that leads to lasting repercussions.