One who is a nonconformist or who does not recognize the authority of others.
A member of the organized heretic movement Brethren of the Free Spirit in opposition of the Catholic Church from the 13th to 15th centuries.
A disbeliever, a denier: someone who rejects or disbelieves in God as per Islam (Arabic: الله Allāh) or the tenets of Islam; or more broadly any non-Muslim.