In Esther 8:9; 9:3 (RSV, "governor") it denotes a Persian prefect "on this side" i.e., in the region west of the Euphrates. It is the modern word Pasha .
In Acts 13:7,8,12; 18:12 , it denotes a proconsul; i.e., the governor of a Roman province holding his appointment from the senate. The Roman provinces were of two kinds, (1) senatorial and (2) imperial. The appointment of a governor to the former was in the hands of the senate, and he bore the title of proconsul (Gr. anthupatos). The appointment of a governor to the latter was in the hands of the emperor, and he bore the title of propraetor (Gr. antistrategos).