From Longman Dictionary of Contemporary Englishunletteredun‧let‧tered /ʌnˈletəd $ -ərd/ adjective formal STUPID/NOT INTELLIGENTunable to read, or uneducated SYN illiterate
Examples from the Corpus
unlettered• Their ideas gain plausibility amongst the idle, the envious and the unlettered.• His lifelong political rival, the charismatic, unlettered Eric Gairy, mocked Blaize's kindly manner as weakness.• The first time I met this creature she was an unlettered half-caste peasant who smelt of stale sweat and dead chickens.• How could the testimony of an unlettered rustic stand against the authority of an Aristotle? 