trump card
noun /ˈtrʌmp kɑːd/
/ˈtrʌmp kɑːrd/
- (also trump)(in some card games) a card that belongs to the suit (= one of the four sets in a pack of cards) that has been chosen for a particular game to have a higher value than the other three suits
- something that gives you an advantage over other people, especially when they do not know what it is and you are able to use it to surprise them
- He was able to get what he wanted without having to play his trump card.
- Many private schools use small classes as their trump card in marketing campaigns.