nonconformist

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One who does not conform to, or refuses to be bound by, accepted beliefs, customs, or practices.
• noun A member of a Protestant church not observing the doctrines, usage, or polity of a national or established church, especially the Church of England.

from The Century Dictionary.

• noun One who does not conform to some law or usage, especially to some ecclesiastical law.
• noun Specifically, in English history, one of those clergymen who refused to subscribe the Act of Uniformity passed in 1662, demanding “assent and consent” to everything contained in the Book of Common Prayer, and by extension any one who refuses to conform to the order and liturgy of the Church of England. See dissenter, 2.
• noun In entomology, the noctuid moth Xylina zinckeni: an English collectors' name, applied in distinction from X. Conformis.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who does not conform to an established church; especially, one who does not conform to the established church of England; a dissenter.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Someone who does not conform to accepted beliefs, customs or practices.
• adjective Not conforming to established customs etc.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective not conforming to some norm or socially approved pattern of behavior or thought
• noun someone who refuses to conform to established standards of conduct
• noun a Protestant in England who is not a member of the Church of England
• adjective not conforming to established customs or doctrines especially in religion