COMMON Your trump card is something which gives you an important advantage over other people and makes it very likely that you will succeed. After only two days, the distribution of goods was suffering: and that is the railwaymen's trump card. He said that the measure was his trump card in his plan to prevent electoral fraud. Note: You can say that someone holds the trump card when they have an advantage like this. In terms of passion and commitment, Ireland held every trump card. Note: If someone plays their trump card, they do something unexpected which gives them an important advantage over other people. She could threaten to play her trump card, an autobiography that would embarrass many important people. Note: In card games such as whist and bridge, one of the four suits is chosen as trumps for each hand. Cards of that suit then rank higher than cards of the other three suits.