Final answer:
A preferred provider organization (PPO) is a medical provider who has negotiated with healthcare professionals to accept a discounted fee at the time the service is performed.
Step-by-step explanation:
A medical provider who has negotiated with healthcare professionals to accept a discounted fee at the time the service is performed is called a Preferred Provider Organization (PPO). PPOs are a type of health insurance plan that allows patients to visit any healthcare provider they choose, but they offer a discounted rate if the provider is part of their network. This allows patients to have more flexibility while still receiving some cost savings.