If a piece of writing is unreadable, it is impossible to read because the letters are unclear, especially because it has been damaged in some way. if contracts are unreadable because of the microscopic print = illegible
disapproval If you use unreadable to describe a book or other piece of writing, you are criticizing it because it is very boring, complicated, or difficult to understand. For some this is the greatest novel in the world. For others it is unreadable = unintelligible
If someone's face or expression is unreadable, it is impossible to tell what they are thinking or feeling. He looked back at the woman for approval, but her face was unreadable. = impenetrable