As adjectives the difference between indecipherable and undecipherable. is that indecipherable is not decipherable; impossible to decode, read, understand or comprehend while undecipherable is not easily deciphered; difficult to read.

What does indecipherable mean?

: incapable of being deciphered indecipherable writing an indecipherable message.

What part of speech is the word indecipherable?

As detailed above, 'indecipherable' is an adjective. Adjective usage: The doctor's handwriting was indecipherable.