a playing card that does not have any particular value but that can be used to represent any other card

The joker is a wild card that substitutes for any other card to complete a winning hand. 鬼牌可以作为百搭牌替代任何其他一张牌从而帮助赢得一局。

in computers, a symbol that has no particular meaning of its own so that its space can be filled by any real character that is necessary

The wild cards are represented here by asterisks. 这里通配符用星号来表示。

someone who is allowed to take part in a competition, even though they have not achieved this in the usual way, for example by winning games

Phillips is hoping for a wild card entry to the championships. 菲利普斯希望得到外卡参加锦标赛。

someone or something whose behaviour is sometimes unexpected

The wild card in this election is the Green Party - no one knows exactly how much support they will get. 本次选举中无法预料的是绿党——没人确切知道他们会获得多少支持。