non-printing
/nɒnˈprɪntɪŋ/adjective
That does not print or is not printed; specifically (a) Printing designating an area of a plate that does not transfer ink to the paper when printing; (b) Computing designating a character in a text which either does not manifest or is represented as a blank space when the text is printed.
Origin
Mid 19th century. From non- + printing.