illiterate

Unable to read and write.

About half of the population in Ethiopia is illiterate.

If publique Aſſemblies of Divines cannot agree upon a right vvay, private Conventicles of illeterate men, vvill ſoon finde a vvrong. Bivious demurres breed devious reſolutions. Paſſengers to heaven are in haſte, and vvill vvalk one vvay or other.

Having less than an expected standard of familiarity with language and literature, or having little formal education.

Ignorant and ſuperſtitious wretches meaſure the actions of letterd and philoſophical men by the tattle of their nurſes or illiterate parents and companions, or by the faſhion of the country : and people of differing religions judge and condemn each other by their own tenents ; when both of them cannot be in the right, and it is well if either of them are.

He's illiterate […] Seriously, how did he get into RI?

Not conforming to prescribed standards of speech or writing.

Now (exc. in Nautical language, see b) it is only dialectal or an illiterate substitute for lie, its identity of form with the past tense of the latter no doubt accounting largely for the confusion.

Ignorant in a specified way or about a specified subject.

economically illiterate, emotionally illiterate

An illiterate person, one either not able to read and write or not knowing how.

We might also provide education plus reading and writing services to adult illiterates.

A person ignorant about a given subject. (The relevant subject is usually named as a noun adjunct.)

Their government is run by business illiterates.

Sometimes a mathematical illiterate is called an innumerate.