Merriam-Webster Collegiate Dictionary - federalist

 noun  Date: 1787  1. an advocate of federalism: as  a. often capitalized an advocate of a federal union between the American colonies after the Revolution and of the adoption of the United States Constitution  b. often capitalized world ~  2. capitalized a member of a major political party in the early years of the United States favoring a strong centralized national government  • ~ adjective, often capitalized