A tour de force is an impressive or amazing feat, like climbing Mount Everest or recording a classic album.
In French, this term means "feat of strength," and that's pretty close to what it means in English — a tour de force is an astounding accomplishment or feat. Critics often refer to a great new movie as a tour de force. A record-breaking performance by an athlete is a tour de force. Important speeches, songs, books, TV shows, or ideas can all be called tours de force. A tour de force isn't just good; it's magnificent.