loyalist

Short definition from Wiktionary

Noun

1. 1
   A person who is loyal to a cause, generally used as a political affiliation.
2. 2
   A person from the 13 Colonies (of British North America from the eastern seaboard of mainland North America) who was in favor of remaining in the British Empire during the American Revolution.
3. 3
   Abbreviation of United Empire Loyalist.
4. 4
   A supporter of keeping Northern Ireland under British rule instead of unification with Ireland, usually from a Protestant background.

Proper noun

1. 1
   A township municipality in Lennox and Addington County, Ontario, Canada.