Not teachable.

Someone who cannot be taught.

The quality of being unteachable.

plural of unteachable

The state or condition of being unteachable.

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

present participle of unteach

Third-person singular simple present indicative form of unteach

plural of unteacher

(derogatory) A popular teacher who focuses on fun activities but lacks pedagogical rigor. / Someone who helps others unlearn or overcome unhealthy social conditioning.