What does 'the departure' mean in 2 Thessalonians 2?
In 2 Thessalonians 2, 'the departure' means the departure of the body of Christ—the church—before the man of sin is revealed. It is the Rapture: the church hears a trumpet call, and in an instant believers are gone, which is the blessed hope Paul mentions.
Les explains that many refute the doctrine of the Rapture because the word Rapture is not in the English New Testament. He notes that the German translation uses the word Rapture, meaning a calling out. In earlier translations of 2 Thessalonians chapter 2, before the man of sin can be revealed, before the Antichrist comes on the scene, there has to be the departure. When asking departure of who or what, he answers: the departure of the body of Christ. This fits the trumpet call to come up hither, the archangel's shout, and the sudden disappearance of those who know the Lord. John's trumpet from heaven is pictured as a symbolic view of what will happen to the church. After the church age has ended, the church is over, and the remaining things are left on the scene. This is the blessed hope Paul talks about in Titus chapter 2.