The term 'PSYCHIATRIST's Appt.' can be summarized as a SESSION with a PSYCHIATRIST, which is a medical doctor who specializes in mental health. A PSYCHIATRIST is trained to diagnose and treat mental illnesses, and they often provide counseling and therapy to their patients. The crossword solution for this term is 'SESS, ' which stands for 'SESSION.' A SESSION with a PSYCHIATRIST typically involves discussing the patient's mental health issues and developing a treatment plan.