After several years of antipsychotic treatment, a patient develops repetitive, purposeless movements of the mouth, tongue, and face, with a gradual onset that developed slowly over time rather than suddenly. What is this?

This is tardive dyskinesia: repetitive, purposeless involuntary movements affecting the mouth, tongue, and facial muscles, with the characteristic later, more gradual ('tardive') onset after long-term antipsychotic exposure, exactly as described. It is not acute dystonia, which by its later, more gradual onset and characteristic repetitive quality differs from an early-onset, sustained spasm. It is not akathisia, which presents as a subjective and objective restlessness rather than repetitive oral and facial movements. And it is not a catatonic stereotypy, which has a different, non-oral distribution and can occur independently of any medication exposure.