unprintable

adj

1. (not-comparable)Not printable; obscene, or unable to be displayed textually.

   “Once a neighbor complained that a Gilbreth had called the neighbor's boy a son of an unprintable word.”

noun

1. Something that is not printable.

   “LabVIEW will interpret one- or two-character codes following the backslash character, as shown in Table 2.1. You can also enter unprintables by simply typing them into the string.”