The federal government defines a beneficiary as a “person who has health care insurance through the Medicare or Medicaid programs,” see Glossary, www.Medicare.gov.
An enrollee is an individual enrolled in a managed healthcare plan. The term usually applies to the subscriber or person who has the coverage in the first place rather than to their dependents, but the term is not always used that precisely.
In contrast, a “member” is an individual covered under a managed care plan and may be either the subscriber or dependent. Gillian I. Russell, Terminology, in FUNDAMENTALS OF HEALTH LAW 1, 14, 27 (American Health Lawyers Association 5th ed., 2011).