a person who maintains that God is one being, rejecting the doctrine of the Trinity.
2.
( initial capital letter ) a member of a liberal religious denomination founded upon the doctrine that God is one being, and giving each congregation complete control over its affairs. Compare Unitarian Universalism.
3.
an advocate of unity or centralization, as in government.
adjective
4.
( initial capital letter ) pertaining to the Unitarians or their doctrines; accepting Unitarianism; belonging to the Unitarians.