ˈwild ˌcard noun [countable]

1. a playing card that can represent any other card

2. someone whose behaviour or effect on a situation is difficult to guess

3. a player who is a wild card or who is given a wild card is chosen for a competition although they have not previously done well enough to take part

4. technical a symbol that can represent any letter in some computer instructions

[TahlilGaran] Dictionary of Contemporary English ▲

wild card
1.
someone or something that you do not know much about and whose behaviour in the future you cannot be certain of.
The real wild card is the undecided vote, which accounts for 18 to 25 percent of the electorate.

The company is fast gaining a reputation as the wild card of Wall Street because of violent fluctuations in its profits.

2.
if someone gets a wild card or is a wild card in a sports competition, they are allowed to enter the competition without passing the usual tests.
She was included in the European team as a wild card.

[TahlilGaran] English Idioms Dictionary ▲

wild-card
a wild card - if someone gets a wild card or is a wild card in a sports competition, they are allowed to enter the competition without passing the usual tests.
Connors, the five-times champion, is among eight wild-card entries to the US Open in New York next month.
(always before noun)

[TahlilGaran] English Idioms Dictionary ▲