tetrarch UK /ˈtɛtɹɑːk/US /ˈtɛtɹɑɹk/noun 3adjective 1forms 1 noun3 •A governor or ruler of a quarter of a country, especially of a fourth part of a province in or client state of Ancient Rome. •Each of the four members of a jointly ruling tetrarchy, notably of the Roman Empire since Diocletian. •An officer in charge of a fourth part of a phalanx in Ancient Greece. adjective1 •Having four vascular strands in a fibrovascular cylinder or stele. formstetrarchs
