n. a conventional antipsychotic agent of the piperazine phenothiazine class. It is used for the treatment of schizophrenia, and its efficacy and side effects are similar to those of other phenothiazines. As with all phenothiazines, long-term use may be associated with the production of tardive dyskinesia or other neuromuscular deficits. U.S. trade name: Trilafon.