Webster's Revised Unabridged Dictionary · 1913

isolationist

isolationist (ī`so*lā"shun*ist) , noun

A proponent or supporter of isolationism; one who is isolationistic.

isolationist , adjective

1.
of or pertaining to isolationism.
2.
Favoring or supporting isolationism; -- of people.

Also: isolationistic