wild card
noun
1- a playing card that can have any value, suit, colour, or other property in a game at the discretion of the player holding it（由持牌人自由决定牌值、花色等的）百搭牌, 变牌。
1.1
- a person or thing whose influence is unpredictable or whose qualities are uncertain未知（或不可预料）的人（或事）, 未知数。
1.2
- Computing a character that will match any character or sequence of characters in a search【计算机】通配符。
1.3
- an opportunity to enter a sports competition without having to take part in qualifying matches or be ranked at a particular level外卡（指无需参加资格赛或排名赛即可参加体育比赛的机会）。
1.4
- a player or team given such an opportunity持外卡参赛的选手（或运动队）。