The Nuttall Encyclopedia
A designation applicable to all monotheists in religion, including Jews and Mohammedans, but generally and more specially applied to those who deny the Church doctrine of the Trinity, and in particular the divinity of Christ, and who have at different times and in different countries assumed an attitude, both within the pale of the Church and outside of it, of protestation against the opposite orthodox creed in the interests of rationalistic belief; the name is also employed in philosophy to designate those who resolve the manifold of being into the operation of some single principle.
Wood, James, ed. Entry for 'Unitarians'. The Nuttall Encyclopedia. https://www.studylight.org/encyclopedias/eng/nut/u/unitarians.html. Frederick Warne & Co Ltd. London. 1900.