1) a tetrarch
    1a) a governor of the fourth part of a region. Thus Strabo states
        that Galactia was formerly divided into three parts, each one
        of which was distributed into four smaller subdivisions each
        of which was governed by a tetrarch. Strabo relates that
        Thessaly, before the time of Philip of Macedon, had been
        divided into four tetrarchies, each having its own tetrarch.
    1b) the governor of a third part or half a country, or even a
        ruler of an entire country or district provided it were of
        comparatively narrow limits; a petty prince. Thus Antony made
        Herod (afterwards king) and Phasael, sons of Antipater,
        tetrarchs of Palestine. After the death of Herod the Great,
        his sons, Achelaus styled an ethnarch but Antipas and Philip
        with the title of tetrarchs, divided and governed the kingdom
        left by their father.