If you’re looking at the French term, pièce de résistance, it’s first valuable to know how to pronounce it. It shouldn’t be pronounced the way piece and resistance are pronounced in English. Instead the first word should sound similar to pee-ess, de should be pronounced as duh, and resistance is best pronounced as ree-sist-tahnse. The term is a direct steal from French, first used in English in the mid 19th century, literally meaning piece of resistance, which does little to explain it as an idiomatic expression.
The word resistance gives us some clues to the meaning od the phrase, in the sense that resistance can mean holding back something. A sentence like “She managed to resist telling him all the new gossip,” is the sense in which resistance in pièce de résistance should be understood. When first used, it meant the crowning moment or ultimate part of a meal.
While you could delight your guests with many fine dishes, you hold back a final, extremely impressive dish as your pièce de résistance. This would be something that would take extraordinary time, effort and skill to produce and would or hopefully should completely wow your guests. It would be foolish to start a meal with the best dish, since nothing else could compare fully with the wonder of it. Instead the final course or dessert, such as chocolate soufflés or a twelve-layer cake would constitute the pièce de résistance.
Since its original use, the phrase has come to mean the crowning moment, the ultimate thing, the most impressive thing, or the most memorable thing. This can apply to collections, where a certain piece of the collection is much more favorable than the others by being more ancient, more beautiful, and more rare. It could also be used in context of describing an actor’s performance, a particular scene in a play or movie, or an aria in an opera that is absolutely standout and memorable.
Sometimes people use the term to describe the highlight of a day, or the highlight of a career. Alan Alda might be described as a formidable actor but his pièce de résistance, or his most memorable performance likely will be remembered as his work on the series M*A*S*H. Occasionally argument exists regarding which work of an artist constitutes the pièce de résistance.
From time to time, the phrase may be used in a sarcastic way to describe not the best but the worst part of a day. A person could be describing an awful day at work, and finish with the following, “But the pièce de résistance was when my boss told me I have to work overtime for the next six weekends.” In this case, the phrase is used to mean memorably bad instead of memorably good.
