The term wildcard character has the following meanings:
In telecommunications, a wildcard character is a
character that may be substituted for any of a defined subset of all possible characters.
In computer (software) technology, a wildcard character can be used to substitute for any other character or characters in a string.
The asterisk (*) usually substitutes as a wildcard character for any zero or more characters, and the question mark (?) usually substitutes as a wildcard character for any one character, as in the MS-DOS, Microsoft Windows and POSIX (Unix) shells. In SQL, the wildcard characters are percent (%) for zero or more characters, and underline (_) for one character. In many regular expression implementations, the period (.) is the wildcard character for a single character.
Source: originally from Federal Standard 1037C and from MIL-STD-188
See also wild cardTelecommunication
Computing