“trump”本身作名词就有“王牌”的意思，自然，“trump card”也就是“王牌；杀手锏；绝招”的意思了。

【例句】
I was pretty sure that I was going to win. I had a trump card.
我很确定我将赢得这场胜利，我有一张王牌。

She could threaten to play her trump card, an autobiography of embarrassing disclosures.
她可能会威胁要拿出她的杀手锏：出自传来爆料糗事。