1. impossible to read or understand; not able to be deciphered

Examples

• The old letter was written in indecipherable handwriting.
• The doctor's prescription was so messy it was almost indecipherable.
• The ancient text remained indecipherable until scholars finally cracked the code.
• His mumbled speech was indecipherable to everyone in the room.
• The faded photograph had indecipherable markings on the back.
• Without the key, the encrypted message was completely indecipherable.