noun
non-alphanumeric character
Computing term for characters that are neither letters nor digits, such as punctuation, symbols, or whitespace.
パスワードには非英数字を含める必要があります。
The password must contain a non-alphanumeric character.
英数字 means alphanumeric characters (letters and digits), while 非英数字 is its negation.
Compound of 非 (non-) + 英数字 (alphanumeric characters).