Unitarian

Part of speech: noun (n.)

1. One who denies the doctrine of the Trinity, believing that God exists only in one person; a unipersonalist; also, one of a denomination of Christians holding this belief.

2. One who rejects the principle of dualism.

3. A monotheist. [R.] Fleming.

Part of speech: adjective (a.)

Of or pertaining to Unitarians, or their doctrines.