wild card

柯林斯詞典

1. N-COUNT If you refer to someone or something as a wild card in a particular situation, you mean that they cause uncertainty because you do not know how they will behave. 未知因素
The wild card in the picture is eastern Europe. 侷勢中的未知因素在東歐。
2. N-COUNT A wildcard is a symbol such as * or ? used in some computing commands or searches in order to represent any character or range of characters. 通配符 (計算機指令中如*或?的符號，用於替代任一字符或系列字符)[計算機]
3. N-COUNT In card games, if a particular card is named as a wild card, the player who holds it may give it any value he chooses. 百搭牌 (牌戯中由持牌人決定牌值的牌)
Look. I have a straight of 3, 4, 6, 7 and the wild card for the 5. 看，我有連著的3，4，6，7，還有一張百搭牌作5。