1) Illegible 2) Incomprehensible 3) Not decipherable 4) Not easily deciphered 5) Not understandable 6) Scribbled 7) Unclear 8) Undecipherable 9) Unreadable Found on https://www.crosswordclues.com/clue/indecipherable
In`de·ci'pher·a·ble adjective Not decipherable; incapable of being deciphered, explained, or solved. -- In`de*ci'pher*a*bly , adverb Found on http://www.encyclo.co.uk/webster/I/40