1A masterpiece — a work of art, film, or craft of outstanding quality, often considered a defining, representative achievement.
その小説は作家の最高傑作と呼ばれている。
That novel is called the author's greatest masterpiece.
美術館にはルネサンス期の傑作が数多く展示されている。
Many Renaissance masterpieces are on display at the museum.
この映画は監督のキャリアの中でも傑作とされる。
This film is regarded as a masterpiece even within the director's career.
2(Jocular, dated) An ironic or humorous way of referring to an absurd blunder or a ridiculously funny mishap.
あの日の彼のスピーチは、間違いだらけの傑作だったね。
His speech that day was a real doozy, full of mistakes.
遅刻の言い訳としては、なかなかの傑作だ。
As excuses for being late go, that one's quite a piece of work.