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brilliant achievement; spectacular feat; splendid accomplishment; remarkable deed
彼女の優勝は快挙だった。
Her victory was a brilliant achievement.
新惑星の発見は歴史的な快挙だ。
The discovery of the new planet is a historic feat.
チームの3連覇はまさに快挙と言えるだろう。
The team's third consecutive championship can truly be called a remarkable feat.