undecipherable

What initially appears abstract contains hidden images: Wild creatures and undecipherable hieroglyphs lurk in the paint.

But they are largely undecipherable to people not educated in the West African Islamic tradition.

For the most part they are undecipherable to people not educated in the West African Islamic tradition — those unable to read Arabic as well as African languages written in modified Arabic script, known as Ajami.

When you find an item, the usual text box identifying it may include a series of undecipherable characters.

This sentence reads smoothly enough today, but back before March 2020, it would have been mostly undecipherable.