Apostate prophet sincerely tries; what is a kafir?

In answer to the video "What Does Kafir (Really) Mean?"

The youtuber here is struggling and wants to know what kafir means. Linguistically, the term in the Quranic language carries a wide range of understanding, from "non believer" to "active enemy of Allah" to "non adherer to the law of Allah, although not necessarily out of the fold of Islam" as in

5:47"And whoever does not judge by what Allah brought down, then those are the kafirun".

The common denominator is that the kafir is someone that willingly denies, conceals the truth and is so adamant to remain in his behavior that should even the best preacher call him to reform, he will not change his ways

2:6"Surely those who kafaru, it being alike to them whether you warn them, or do not warn them, will not yu'minun/safely trust (in the message)".

Here it must be noted, that the kafir label is most often wrongly assumed as generaly refering to all non Muslims yet the Quran itself in many places states that this cannot be the case. It does so, among other things, by exposing the limited knowledge of humans when they begin assuming and conjecturing on other people's spiritual condition. Towards the end of the Prophet's mission when it was thought that a clear line had been drawn between followers and rejecters of Islam, as a major conflict was about to erupt between the Muslims and the Meccans, God states that had it not been for Him withholding their hands from fighting, many Muslims in what was assumed to be the disbelieving camp would have been killed by Muslims 48:25. In other places it quotes members of Jewish and Christian communities joining Islam during their declaration of faith, saying that

28:53"We believe in it surely it is the truth from our Lord; surely we were submitters before this".

There are several such verses, and when one understands the fact that a kafir, one whose spirituality is sealed in Quran terminology is one bent on a willful repetitive misbehavior, then such label cannot be used haphazardly on anyone outside the fold of Islam.

In 57:20 the tiller of the soil is called, without any pejorative implication, a kafir. This is because he literally is "one who covers", when he covers the seed with earth. The night is spoken of as having "covered" (kafara) the earth with darkness. Allah covers, yukaffir, the sins of those who will enter heaven 48:5. In their abstract sense, and as already noted, both the verb and the nouns derived from it have a connotation of "concealing" something that exists as Allah says when He covers/kafara the evil deeds of the people 5:65. When used for someone it has the connotation of "denying" something that is true. It relates to man's deliberate suppression of his inborn cognition of God's existence 7:172, acting against his spiritual senses 76:2,46:26 and innate understanding of good and evil 91:7-8.