1. Health insurance purchasing entity (public or private) that enrolls subscribers or members within a given region, collects premiums, enforces rules that manage health plans, and purchases subscribers’ or members’ insurance from participating health plans. 2. Organization or group of employers that pools resources to buy health care goods and services. Also known as a purchasing group . See consumer health alliances. 3. Formal, mutual arrangement of companies, providers, or institutions, established to further common goals.