Interesting comment on this Greek word - used three times according to Strong's -
Anyway, I believe that “marking” and disfellowshipping are to be treated the same. 2 Thessalonians 3:14-15 says: “But if anyone is not obedient to our word through this letter, keep this one marked, stop associating with him, that he may become ashamed. 15 And yet do not be considering him as an enemy, but continue admonishing him as a brother”. The Greek word which the NWT translates “stop associating with” in 2 Thessalonians 3:14 is the same word used in 1 Corinthians 5:11 for “quit mixing in company with”. Both texts in the Greek language are speaking of someone who is unruly or immoral. Also, notice that 2 Thessalonians 3:15 tells us to, “not be considering him as an enemy, but continue admonishing him as a brother.” A question I have asked many JW’s over the years is, how can we admonish one as a brother if we cut him off as the organization says we should?