trump card

American  

[truhmp kahrd, truhmp kahrd] / ˈtrʌmp ˌkɑrd, ˈtrʌmp ˈkɑrd /

noun

1. Cards. trump.

2. Informal. something that gives one person or group the advantage over another.

   The surprise witness was his trump card.

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trump card Cultural  

1. In general, something capable of making a decisive difference when used at the right moment; in certain card games, trump is the suit designated as having precedence over the others: “The prosecutor was about to win the case, when the defense lawyer produced her trump card: an eyewitness who testified that the accused was nowhere near the scene of the crime.”

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trump card Idioms  

1. A key resource to gain an advantage at the opportune moment, as in That surprise witness was the defense's trump card, or She played her trump card, announcing that the Senator would speak. This expression transfers the trump card of games such as bridge, which can win over a card of another suit, to other kinds of advantage. [Early 1800s]

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Etymology

Origin of trump card

First recorded in 1815–25

Example Sentences

For decades, Iran has held a single geopolitical trump card in its pocket — the ability to shut down oil-tanker traffic in the Strait of Hormuz.

From MarketWatch • Apr. 15, 2026

England rolled out six slow bowling options, with part-timer Joe Root turning out to be an unlikely trump card.

From Barron's • Jan. 24, 2026

Rare earths aren’t Mr. Xi’s only trump card.

From The Wall Street Journal • Oct. 27, 2025

Under pressure, England went to their trump card.

From BBC • Sep. 6, 2025

I did, however, have one trump card left to play, or I thought I did.

From "Boy: Tales of a Childhood" by Roald Dahl