Remember when Wired magazine first launched, and illegibility was a design trend?
From the forbes.com
Predictably, illegibility errors were completely eliminated by e-prescribing.
From the sciencedaily.com
Have your friend alert you of any errors that show when they open it, like illegibility and organization.
From the edition.cnn.com
Sadly, many of the visuals are memorable more for their illegibility and the multiplicity of their colours than the clarity of the message.
From the newscientist.com
The effects of the Collodion process further disturb the body's coherence by making images oscillate between clarity and near illegibility, removing any purchase we usually assume.
From the telegraph.co.uk
Also, mimeographed images were as durable as the paper they were printed on, and didn't bleach to illegibility if exposed to sunlight, the way that dittoed pages did.
From the en.wikipedia.org
More examples
The quality of writing (print or handwriting) that cannot be deciphered
(illegible) (of handwriting, print, etc.) not legible; "illegible handwriting"
The characteristic or quality of being illegible; the quality of being difficult or impossible to read