schism

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

• noun A separation or division into factions.
• noun A formal breach of union within a religious body, especially a Christian church.
• noun The offense of attempting to produce such a breach.

from The Century Dictionary.

• noun Division or separation; specifically, in ecclesiastical usage, a formal separation within or from an existing church or religious body, on account of some difference of opinion with regard to matters of faith or discipline.
• noun The offense of seeking to produce a division in a church.
• noun A schismatic body.

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

• noun (Eccl.) Division or separation
• noun (Eccl.) the separation of the Greek and Roman churches.
• noun (Eccl.) a schism in the Roman church in the latter part of the 14th century, on account of rival claimants to the papal throne.
• noun (Law) an act of the English Parliament requiring all teachers to conform to the Established Church, -- passed in 1714, repealed in 1719.

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

• noun A split or separation within a group or organization, typically caused by discord.
• noun religion A formal division or split within a religious body.
• noun Catholicism a split within Christianity whereby a group no longer recognizes the Bishop of Rome as the head of the Church, but shares essentially the same beliefs with the Church of Rome. In other words, a political split without the introduction of heresy.

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

• noun the formal separation of a church into two churches or the withdrawal of one group over doctrinal differences
• noun division of a group into opposing factions