What is the meaning of Wildcard?

A character that takes the place of any other character or string that is not known or specified.

An uncontrolled or unpredictable element.

An element, often deliberately concealed, which is withheld for contingency.

Alternative form of wild card.

A letter or symbol that substitutes for a generic or poorly identified sound, for example capital C for any or some consonant, or capital V for any or some vowel.

To replace or supplement with a wildcard character to allow matching against a range of possible values.

wildcard

Source: wiktionary.org