42 C.F.R. § 405.400
For purposes of this subpart, the following definitions apply:
Beneficiary means an individual who is enrolled in Part B of Medicare.
Emergency care services means inpatient or outpatient hospital services that are necessary to prevent death or serious impairment of health and, because of the danger to life or health, require use of the most accessible hospital available and equipped to furnish those services.
Legal representative means one or more individuals who, as determined by applicable State law, has the legal authority to enter into the contract with the physician or practitioner on behalf of the beneficiary.
Opt-out means the status of meeting the conditions specified in § 405.410 .
Opt-out period means, with respect to an affidavit that meets the requirements of § 405.420 , a 2-year period beginning on the date the affidavit is signed, as specified by § 405.410(c)(1) or (2) as applicable, and each successive 2-year period unless the physician or practitioner properly cancels opt-out in accordance with § 405.445 .
Participating physician means a "physician" as defined in this section who has signed an agreement to participate in Part B of Medicare.
Physician means a doctor of medicine; doctor of osteopathy; doctor of dental surgery or of dental medicine; doctor of podiatric medicine; or doctor of optometry who is legally authorized to practice medicine, osteopathy, dental surgery, dental medicine, podiatric medicine, or optometry by the State in which he performs such function and who is acting within the scope of his license when he performs such functions.
Practitioner means a physician assistant, nurse practitioner, clinical nurse specialist, certified registered nurse anesthetist, certified nurse midwife, clinical psychologist, clinical social worker, marriage and family therapist, mental health counselor, registered dietitian or nutrition professional, who is currently legally authorized to practice in that capacity by each State in which he or she furnishes services to patients or clients.
Private contract means a document that meets the criteria specified in § 405.415 .
Properly opt-out means to complete, without defect, the requirements for opt-out as specified in § 405.410 .
Properly terminate opt-out means to complete, without defect, the requirements for terminating opt-out as specified in § 405.445 .
Urgent care services means services furnished to an individual who requires services to be furnished within 12 hours in order to avoid the likely onset of an emergency medical condition.
42 C.F.R. §405.400