The term 'Fixed by a Vet' refers to the process of neutering an animal. Neutering is a surgical procedure performed by a veterinarian that removes the reproductive organs of an animal, usually a male dog or cat, in order to prevent reproduction. Neutering is often done for health and behavioral reasons, such as reducing the risk of certain types of cancer and decreasing aggressive behavior. Neutering also helps to reduce pet overpopulation, which is a major problem in many areas.