1. A physician or, less often, a dentist who specializes in the practice of medicine involving the use of drugs or other agents that cause insensibility to pain: Before Robert's root canal operation, Dr. Jones, the dentist and a trained anesthesiologist, administered a local medication so the patient would feel no pain.
2. A physician who specializes in the administration of pain killers in order to prevent or to cause an insensibility to pain during surgery, birth labor and delivery, or other medical procedures: An anesthesiologist has a medical doctorate whereas an anesthetist does not. An anesthetist is a nurse, or technician, trained to administer anesthetics.