adjective
Espousing a unitary view of something
noun
(Christianity) A Christian who denies the doctrine of the Trinity, usually stressing some distinctions between God the Father and God the Son without denying the divinity of Jesus.
(Islam) Synonym of Muwahhid, a Muslim advocating God's strict unity.
(uncommon) Synonym of monotheist, a believer in the unity of God, particularly non-Christians (Muslims, Jews, etc.) discussed from a Christian perspective.
A person who rejects dualism in other contexts.