"Demon possession" is an incorrect translation for what should be translated as "demonization."
For a Non-Christian, many examples in the Bible portray it as a condition where a demon inhabits a human
being, in part or whole, and controls the human being's mind, body or, in rare cases, his will.
When referring to Christians, this definition is debated; but, most theologians would agree that it is more
appropriately seen, at least, as "strong demonic influence."