illegible

adjectives

(of handwriting, print, etc.) not legible
"illegible handwriting"
illegible
is derived from
illegibility
antonym
legible
is similar to
(of a manuscript) defaced with changes
"foul (or dirty) copy"
dirty, foul, marked-up
is similar to
not easily deciphered
"indecipherable handwriting"
indecipherable, unclear, undecipherable, unreadable