a person or thing whose behaviour or effect is difficult to predict 行为和结果难以预测的人（或事）◆When it comes to making big changes in an organization, the wild card is the employees' ability to adapt to the new system. 当对一个组织进行大刀阔斧的改革时，难以预测的是员工对新体制的适应能力。
() a symbol that has no meaning of its own and can represent any letter （可以代表任何字母的）通配符◆An asterisk is commonly used as a wild card. 星号常常被用作通配符。◆a wild-card search 通配符搜索