noun
In card games, the suit designated as trumps, or a specific trump card.
スペードが切り札のゲームだ。
It's a game where spades are trumps.
最後の切り札
I played my last trump card and won.
noun
ace up one's sleeve; secret weapon; last resort
Figurative use: a hidden advantage, decisive resource, or final option kept in reserve for a critical moment.
交渉の切り札としてその情報を使った。
He used that information as a trump card in the negotiations.
彼女は最後の切り札をまだ隠している。
She is still hiding her final ace up her sleeve.