1. Someone who rejects the need for a system of government in society and proposes its abolition: "The anarchists at the university campus sought to occupy the offices of the administration and to disrupt the operations of the university."
2. Any one who tries to overthrow a society’s formal system of government or behaves in a generally lawless manner and encourages others to do the same: "Some anarchists wrote a book which suggested ways to overthrow legitimate establishments."