undecipherable

/ˌʌndɪˈsaɪfərəbəl/
adjective
  1. Impossible to read or understand because it is not clear, messy, or in code.
    • The ancient script remained undecipherable for centuries.
    • Her note was so smudged it was undecipherable.
    • The doctor's handwriting was completely undecipherable.
  2. Impossible to interpret or make sense of; confusing.
    • The message was encrypted and undecipherable to anyone without the code.
    • His expression was undecipherable, so I couldn't tell if he was angry.
    • The data from the experiment was undecipherable without the key.