Parthian Empire noun1 •(historical) An ancient empire of West Asia founded as a kingdom by Arsaces I with his 3rd-century-BCE conquest of Parthia (only recently a satrapy of the Seleucid Empire) and subsequently greatly expanded by Mithridates I.The Parthian Empire became involved in an extended period of conflict with the Roman Republic and Empire that lasted for three centuries, until the latter eventually prevailed.
