The abandonment of religious beliefs.
The Bible indicates that there will be a great apostasy during the end times. The “great apostasy” is mentioned in 2 Thessalonians 2:3. The KJV calls it the “falling away,” while the NIV and ESV call it “the rebellion.” And that’s what an apostasy
is: A rebellion, an abandonment of the truth. The end times will
include a wholesale rejection of God’s revelation, a further “falling
away” of an already fallen world..gotquestions.org/great-apostasy
Apostasy is abandoning or deserting the worship and service of God, and actually a rebellion against God himself. A foretold apostasy began to develop less than a century after the Christian congregation was established. (Acts 20:28-30 ; 2 Thess. 2:3,4) Some profess to know and serve God but reject teachings or requirements set out in his word the bible. Therefore, it became increasingly difficult to identify who was truly serving God.
Apostasy are those who have defected from true worship, which began after the death of the apostles, it blossomed and produced the churches of Christendom. Acts 20:29,30