Tetrarch
Easton’s Bible Dictionary
Tetrarch: strictly the ruler over the fourth part of a province; but the word denotes a ruler of a province generally (Matthew 14:1; Luke 3:1,19; 9:7; Acts 13:1). Herod and Phasael, the sons of Antipater, were the first tetrarchs in Palestine. Herod the tetrarch had the title of king (Matthew 14:9).