trump card

剑桥词典

an advantage that makes you more likely to succeed than other people , especially something that other people do not know about
獨有的優勢，獨門法寶；王牌；絕招
Anthea was about to play her trump card - without her signature none of the money could be released . 安西婭準備打出她的王牌——沒有她的簽字，一分錢也不能動。 返回 trump card