I emphasize THE...it is not just any (some) apostasia, it is a SERIOUS apostasia (whatever Paul meant by that word). It was a very significant apostasia - one that Paul expected people to instantly recognize as what he was talking about. In my mind some falling away does not meet a significant apostasia or departing.
Falling away from the truth is very serious. It is also serious that you refuse every Greek dictionary and concordance etc that affirms the word means a defection from the truth, Apostasy. See, you won't accept evidence of the truth not from scripture and not from Greek definition sources. That means you have closed your eyes and won't change your mind.
2Th 2:3 Let no man deceive you by any means: for that day shall not come, except there come
a falling away (apostasia) first, and that man of sin be revealed, the son of perdition;
The word "falling away" is apostasia from where we get the words Apostate and Apostasy. Obviously it means a moral and spiritual religious "departure" not a physical departure.
Don't believe anything that says this event is the rapture. Here are 5 expert sources that prove the "departure" in 2 Thess 2:3 is the Apostasy:
Strong's definition G646
apostasia
ap-os-tas-ee'-ah
Feminine of the same as G647;
defection from truth (properly the state), (“apostasy”) : - falling away, forsake.
Total KJV occurrences: 2
Thayer Definition:
G646 apostasia
1)
a falling away, defection, apostasy
Part of Speech: noun feminine
A Related Word by Thayer’s/Strong’s Number: feminine of the same as G647
Citing in TDNT: 1:513, 88
Total KJV occurrences: 2
Abbott-Smith Manual Greek Lexicon of the New Testament
Apostasia
defection, apostasy, revolt; in late Gk. (MM, Exp., viii; Lft., Notes, 111; Cremer, 308) for cl. ?p?stas?? , freq. in sense of political revolt, in LXX (e.g. Joshua 22:22, 2 Chronicles 29:19, Jeremiah 2:19)
and NT always of religious apostasy: Ac21:21, II Th 2:3.
Liddell and Scott:
A defection, revolt, v.l. in D.H.7.1, J.Vit.10, Plu.Galb.1; esp.
in religious sense, rebellion against God, apostasy, LXX Jo.22.22, 2 Ep.
Th.2.3 .
Winer's Grammar:
Apostasia,
a falling away, defection, apostasy; in the Bible namely, from the true religion: Acts 21:21; 2 Thessalonians 2:3 ; ((Joshua 22:22; 2 Chronicles 29:19; 2 Chronicles 33:19); Jeremiah 2:19; Jeremiah 36
29) 32 Complutensian; 1 Macc. 2:15). The earlier Greeks say Apostasis; see Lob. ad Phryn., p. 528; (Winer's Grammar, 24).