Synonyms for Unlettered (same or very similar meaning)
WordNet sense 1 (having little acquaintance with writing):
analphabeticWordNet sense 2 (not able to read or write):
illiterateWordNet sense 3 (uneducated in general; lacking knowledge or sophistication):
nescient, unenlightened, unlearnedWordNet sense 4 (not having a good education):
uneducatedFrom the ODE community, based on WordNetadd/edit