wild card

柯林斯词典

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. 局势中的未知因素在东欧。
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 (计算机指令中如*或?的符号，用于替代任一字符或系列字符)[计算机]
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 (牌戏中由持牌人决定牌值的牌)
Look. I have a straight of 3, 4, 6, 7 and the wild card for the 5. 看，我有连着的3，4，6，7，还有一张百搭牌作5。