Illiterate, a.
Etymology: [L. illiteratus: pref. il- not + literatus learned. See In- not, and Literal.]
Ignorant of letters or books; unlettered; uninstructed; uneducated; as, an illiterate man, or people.
Syn. -- Ignorant; untaught; unlearned; unlettered; unscholary. See Ignorant. -- Il*lit"er*ate*ly, adv. -- Il*lit"er*ate*ness, n.
Shades of meaning
Fernald has no entry of its own for illiterate; he lists it under ignorant.
Where he writes about it:
Illiterate is without letters and the knowledge that comes through reading. — from ignorant
Unlettered is similar in meaning to illiterate, but less absolute; the unlettered man may have acquired the art of reading and writing and some elementary knowledge; the uneducated man has never taken any systematic course of mental training. — from ignorant