Apostasy is abandoning or deserting the true worship, doctrine, and service of God. It is a rebellion against God.
Apostasy: A “falling away,” usually a deliberate and total abandonment of the faith previously held. Apostate: One who departs from the faith.
Apostasy: (Gr. apostasia) The term literally means 'to stand away from' and is used to refer to ones who ‘stand away from the truth.’ It is abandonment, a rebellion, an apostasy, a refusal to accept or acknowledge true worship.
An apostate's defection from the faith may be intellectual, as in the case of Ernst Haeckel, who, because of his materialistic philosophy, publicly and formally renounced Christianity and the church. Then, there is Dr. Bart D. Ehrman who has rejected Christ because of his doubt in the trustworthiness of the Bible and the problem of evil, and so he has actively worked in opposition to Christ for 20+ years. It may also be moral and spiritual, as with Judas, who for filthy silver pieces basely betrayed his Lord.
The Greek word here - ἀποστήσονται apostēsontai - is that from which we have derived the word “apostatize,” and would be properly so rendered here. The meaning is, that they would “apostatize” from the belief of the truths of the gospel.
Bart D. Ehrman is one of the most renowned and controversial Bible scholars in the world today. However, Ehrman is also a world-renowned New Testament textual and early Christianity scholar, who literally refers to himself as the "Happy Agnostic."