كفر
Kafara
To deny in declared words that God is God, that Muhammad is His Prophet, or that the Quran is wholly God’s truth and revelation.
What it means
The root k-f-r means to cover or to deny. In religious use kafara means to reject faith openly. Faruqi gives the sense of solemnly saying that God is not God, or that He lacks any of His attributes, that Muhammad (peace be upon him) is not the Prophet of God, or that anything in the Quran is not verbatim truth and revelation from God. The noun is kufr and the one who does it is a kāfir. Jurists urge great care in applying it. A hadith in Sahih al-Bukhari and Sahih Muslim warns that if a man calls his brother a kāfir, the charge falls on one of them.
Often misunderstood as
It is rendered “infidel” in older English, a word that carries a sense of contempt that the Arabic term does not have.
Term and Arabic as listed in Ismail al Faruqi, Toward Islamic English (International Institute of Islamic Thought, 1995), p. 45, listed as KAFARA. The definition is restated here.