Someone who cannot be taught.

Not teachable.

plural of unteachable

The quality of being unteachable.

present participle of unteach

(transitive) To cause (someone) to unlearn; to make (someone) forget something they have been taught, or recognize it as erroneous, etc.

Third-person singular simple present indicative form of unteach

The state or condition of being unteachable.

In an unteachable manner.

plural of unteacher