'Turn' in the Bible

Take care, brothers and sisters, that there not be in any one of you a wicked, unbelieving heart [which refuses to trust and rely on the Lord, a heart] that turns away from the living God.

and then have fallen away—it is impossible to bring them back again to repentance, since they again nail the Son of God on the cross [for as far as they are concerned, they are treating the death of Christ as if they were not saved by it], and are holding Him up again to public disgrace.

Now, we do not belong to those who turn back and are destroyed, but to those who have faith and are saved.

See that ye refuse not him that speaketh. For if they escaped not who refused him that spake on earth, much more shall not we escape, if we turn away from him that speaketh from heaven: