To take something offline is to move it out of the current meeting: the detail two people care about continues later, so the other eight get their agenda back. Despite the word, no internet is involved; offline here just means “not in this room, not right now”.
It is one of the most defensible pieces of meeting jargon because it protects everyone’s time when actually done. The failure mode matches circle back: offline conversations that never happen. Same fix: an owner and a time, in the notes.