A trump card in card games—a card that outranks others (the trump suit or card).
彼は最後の一手で切り札を出して勝負を決めた。
He played his trump card in the final move and decided the game.
このゲームではスペードが切り札だ。
In this game, spades are trumps.
A decisive asset or secret weapon—an ace up one's sleeve; a final advantage used in negotiations or conflict.
新製品は会社の切り札として市場に投入された。
The new product was launched as the company's trump card in the market.
彼女は交渉で切り札を使い、条件を有利に変えた。
She used her ace card in the negotiations and changed the terms in her favor.
その戦略は最後の切り札になるかもしれない。
That strategy might become the final trump card.