It's often used to describe things like:
* Writing: A language or script that is so old or unfamiliar that it cannot be read.
* Codes: A cipher or code that is too complex or intricate to be broken.
* Speech: Mumbling, whispering, or a language you don't understand.
* Symbols: Marks or images that lack a clear meaning.
Here are some examples of how "undecipherable" might be used:
* "The ancient inscription on the tomb was undecipherable, leaving historians baffled."
* "The spy's message was written in an undecipherable code."
* "His mumbling was undecipherable, so I had no idea what he was trying to say."
* "The artist's abstract paintings were filled with undecipherable symbols."