Unreadable is an adjective used to describe something that cannot be read or is difficult to read. Synonyms for the word include illegible, indiscernible, incomprehensible, unintelligible, unfathomable, inscrutable, indecipherable, and undecipherable. These words are often used to describe written or printed material, such as handwriting, text on a page, or a computer screen. Something may be unreadable due to a lack of clarity, poor penmanship, or technical issues with the text. Additionally, a lack of knowledge or understanding of a language, code, or cipher may also render something unreadable. It is important to consider the context in which the word is used to determine the appropriate synonym.