a person who has withdrawn from a political group and joined with a few others to form a dissident group
Word Origin
C19: originally applied to members of the British House of Commons who withdrew from the Liberal party (1866); alluding to the cave of Adullam in the Bible, to which David and others fled (1 Samuel 22: 1–2)
adullamite in the Bible
an inhabitant of the city of Adullam (Gen. 38:1, 12, 20).