Breakaway faction

WordNet Word definitions in WordNet
n. a faction or sect that has broken away from its parent organization

Wiktionary Word definitions in Wiktionary
n. A group of members of a political party or of a similar organisation who have decided to create their own organisation.

Longman Dictionary of Contemporary English Word definitions in Longman Dictionary of Contemporary English
noun EXAMPLES FROM OTHER ENTRIES ▪ They are a hard-line conservative splinter group of the Republican Party. EXAMPLES FROM CORPUS ▪ A week before the election a splinter group of the Moro National Liberation Front had taken several nuns captive. ▪ According ...