Douglas Harper's Etymology Dictionary
1831, from French pièce de résistance, originally "the most substantial dish in a meal." Lit. "piece of resistance;" there seems to be disagreement as to the exact signification.
Wiktionary
n. (context idiomatic English) A masterpiece; the most memorable accomplishment of one’s career or lifetime.
WordNet
n. the outstanding item (the prize piece or main exhibit) in a collection [syn: collector's item, showpiece]
the most important dish of a meal
Usage examples of "piece de resistance".
The piece de resistance was Ungo-Bungo the ferocious ape-man, captured in the Congo at a cost of twenty-seven lives.
The piece de resistance of his imagery was the dynamic convergence-zone display.
But the piece de resistance of the collection, the object I'd give my few remaining teeth to get in my hands, is the log of the derelict they found in the ice.
After the initial amazement faded, Gaskill rushed from room to room, searching for the piece de resistance of the collection.
Up by the highway, Jerzy had the piece de resistance: a jar full of ground ginger.
The latter were gorging themselves upon food and, under the very noses of their white masters, preparing the gruesome feast which is the PIECE DE RESISTANCE that follows a victory in which the bodies of their slain enemies fall into their horrid hands.