wild card

/W AY1 L D K AA0 R D/
noun
  1. 1

    In card games, a card that can be assigned any value or used to substitute for any needed card.

  2. 2

    A competitor or team that is allowed to compete in a tournament despite not reaching the normal standards to qualify for inclusion.

    โ€œKye Sun-Hui won an Olympic gold medal in Judo, despite being a wild card.โ€

  3. 3

    A character that substitutes for other characters in regular expressions and globbing

Source: https://en.wiktionary.org/wiki/wild%20card