Wiktionary
indecipherability
n. quality of being indecipherable.
Usage examples of "indecipherability".
It was pockmarked and rusted to the edge of indecipherability, but after a couple of years in Maggody, most everything and everybody is.
It was well-made and there might have been an inscription on it once, but it had long ago been worn into indecipherability by sheer use.