One of the rulers in an oligarchy.

Roget 745: master, padrone; lord, lord paramount; commander, commandant; captain; chief, chieftain; sirdar^†, sachem, sheik, head, senior, governor, ruler, dictator; leader etc. (director) 694; boss, cockarouse^†, sagamore, werowance^†.    lord of the ascendant; cock of the walk, cock of the roost; gray mare; mistress.    potentate; liege, liege lord; suzerain, sovereign, monarch, autocrat, despot, tyrant, oligarch.    crowned head, emperor, king, anointed king, majesty, imperator [Lat.], protector, president, stadholder^†, judge.    ceasar, kaiser, czar, tsar, sultan, soldan^†, grand Turk, caliph, imaum^†, shah, padishah^†, sophi^†, mogul, great mogul, khan, lama, tycoon, mikado, tenno [Jap.], inca, cazique^†; voivode^†; landamman^†; seyyid^†; Abuna^†, cacique^†, czarowitz^†, grand seignior.    prince, duke etc. (nobility) 875; archduke, doge, elector; seignior; marland^†, margrave; rajah, emir, wali, sheik nizam^†, nawab.    empress, queen, sultana, czarina, princess, infanta, duchess, margravine^†; czarevna^†, czarita^†; maharani, rani, rectrix^†.    regent, viceroy, exarch^†, palatine, khedive, hospodar^†, beglerbeg^†, three-tailed bashaw^†, pasha, bashaw^†, bey, beg, dey^†, scherif^†, tetrarch, satrap, mandarin, subahdar^†, nabob, maharajah; burgrave^†; laird etc. (proprietor) 779; collector, commissioner, deputy commissioner, woon^†.    the authorities, the powers that be, the government; staff, etat major [Fr.], aga^†, official, man in office, person in authority; sircar^†, sirkar^†, Sublime Porte.    [Military authorities] marshal, field marshal, marechal^†; general, generalissimo; commander in chief, seraskier^†, hetman^†; lieutenant general, major general; colonel, lieutenant colonel, major, captain, centurion, skipper, lieutenant, first lieutenant, second lieutenant, sublieutenant, officer, staff officer, aide-de-camp, brigadier, brigade major, adjutant, jemidar^†, ensign, cornet, cadet, subaltern, noncommissioned officer, warrant officer; sergeant, sergeant major; color sergeant; corporal, corporal major; lance corporal, acting corporal; drum major; captain general, dizdar^†, knight marshal, naik^†, pendragon.    [Civil authorities] mayor, mayoralty; prefect, chancellor, archon, provost, magistrate, syndic; alcalde^†, alcaid^†; burgomaster, corregidor^†, seneschal, alderman, councilman, committeeman, councilwoman, warden, constable, portreeve^†; lord mayor; officer etc. (executive) 965; dewan^†, fonctionnaire [Fr.].    [Naval authorities] admiral, admiralty; rear admiral, vice admiral, port admiral; commodore, captain, commander, lieutenant, ensign, skipper, mate, master, officer of the day, OD; navarch^†.    ... show more

Dutch: oligarch
Polish: oligarcha