Learn how to say Unitarianist correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word Unitarian:
a person who asserts the unity of God and rejects the doctrine of the Trinity.
a member of a Church or religious body maintaining this belief and typically rejecting formal dogma in favour of a rationalist and inclusivist approach to belief.
relating to the Unitarians.
late 17th century: from modern Latin unitarius (from Latin unitas ‘unity’) + -an