The word appears in Acts 17:6, where Jason and the Christians are dragged before city authorities with the accusation: "These men who have turned the world upside down (anastatoo) have come here also!" This is one of the most accurate and ironic descriptions of the Gospel's power: it genuinely does overturn existing orders — of sin, of death, of human pride. Paul's opponents in Galatia also "trouble" (anastatoo) the churches (Galatians 5:12). The Gospel is not meant to settle the comfortable but to unsettle the settled.
Anastatoo means to cause an uprising, to unsettle or disturb profoundly, to turn upside down. It describes the kind of disruption that challenges existing order and produces social or spiritual upheaval.