trump card

[ truhmp kahrd truhmp kahrd ]

noun

1. Cards. trump ¹( def 1a ).
2. Informal. something that gives one person or group the advantage over another:

   The surprise witness was his trump card.

trump card

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.”

Word History and Origins

Origin of trump card¹

First recorded in 1815–25

Idioms and Phrases

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]