Unitarian

A Christian who does not believe in the traditional doctrine of the Trinity.

A follower of Unitarian Universalism; or a member of a Unitarian Universalist Church in North America who adhered to, or identifies with, the Unitarian part of that church prior to consolidation in 1961.

(rare) A Muslim, Jew or other kind of monotheist who is not a Christian.

A member of a political movement advocating a unitary state (where a country is governed as one single unit), especially the Unitarios of nineteenth century Argentina (known as the Unitarian Party in English).