The Collaborative International Dictionary of English v.0.48:
Unitarianism \U`ni*ta"ri*an*ism\, n. [Cf. F. unitairianisme.] The doctrines of Unitarians. [1913 Webster]WordNet (r) 3.0 (2006):
Unitarianism n 1: Christian doctrine that stresses individual freedom of belief and rejects the Trinity