Undecipherable (adjective)

Impossible to read or understand; not decipherable.

Origin:

From un- (not) + decipherable (able to be deciphered or understood).

Examples:

1. The ancient text was undecipherable and required the help of a specialist to be translated.
2. The handwriting on the note was so bad that it was undecipherable.
3. The code was undecipherable, even for the most experienced cryptographer.
4. The message on the computer screen was undecipherable due to a technical error.
5. The message received through morse code was undecipherable due to poor signal strength.