The word "letterless" refers to something that has no letters or written communication associated with it. Synonyms for this word can include words such as unscribed, unmarked, blank, empty, or non-written. These synonyms all convey the same general meaning of lacking any form of written communication. However, in certain contexts, some synonyms may be more appropriate than others. For example, the word "blank" might be used to describe a page that has no writing on it, while "unscribed" might be used to describe an entire document or manuscript that was never written in the first place. Ultimately, the choice of synonym depends on the specific context in which the word is being used.