Kufar is an Arabic term used in a Islamic doctrinal sense, usually translated as "unbeliever" or "disbeliever". The term refers to a person who rejects God or who hides, denies, or covers the "truth". Even though labeling infidelity is referred usually to Islam

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Kufrul-'Inaad:
Disbelief out of stubbornness. This applies to someone who knows the truth and admits to knowing the truth and admits to knowing it with his tongue, but refuses to accept it