Noun
metacharacter (plural metacharacters)
(computing) A character used to signify something other than its literal form, such as the asterisk when used as a wildcard.
Each character in a regular expression (that is, each character in the string describing its pattern) is understood to be a metacharacter (with its special meaning), or a regular character (with its literal meaning). Source: Internet
With this syntax, a backslash causes the metacharacter to be treated as a literal character. Source: Internet