Kafir (Arabic: كافر kāfir, plural كفّار kuffār) is an Arabic term used in a Islamic doctrinal sense, usually translated as "unbeliever," "disbeliever," or "infidel." The term refers to a person who rejects God or who hides, denies, or covers the "truth."
Read more about Kafir: Etymology, Types of Disbelief, Muslim Relations, Use Outside Islam