Definition of "Elector"

In one of the conflicts, the [Holy Roman] emperor himſelf was put to flight, and very near being made priſoner by the elector of Saxony.

1788, Publius [pseudonym; James Madison], “Number XIX. The Subject [the insufficiency of the present confederation to preserve the Union] Continued, with Farther Examples.”, in The Federalist: A Collection of Essays, Written in Favour of the New Constitution, […] , volume I, New York, N.Y.: […] J. and A. M‘Lean, […], page 117

[T]he seven Imperial electors who chose the [Holy Roman] emperor controlled him by the pledges exacted from him as the price of his election. These electors were the king of Bohemia, the rulers of Saxony, Brandenburg, and the Palatinate, and the "spiritual electors"—the archbishops of Cologne, Trier, and Mainz.

1961, Will Durant, Ariel Durant, “Imperial Armageddon: 1564–1648”, in The Age of Reason Begins: A History of European Civilization in the Period of Shakespeare, Bacon, Montaigne, Rembrandt, Galileo, and Descartes: 1558–1648 (The Story of Civilization; 7), New York, N.Y.: Simon & Schuster, page 538

Hanover, seat of the electors, was an attractive small town set on the River Leine. [...] The electoral court was in residence at Herrenhausen only between May and October, so that by the beginning of November 1709 the only activity was in one of the private wings where Caroline of Ansbach, wife of the elector’s heir, had chosen to give birth to her second child.

1995, Veronica P. M. Baker-Smith, “An Electoral Family”, in A Life of Anne of Hanover, Princess Royal (Publications of the Sir Thomas Browne Institute Leiden; no. 13 (New Series)), Leiden, New York, N.Y.: E[vert] J[an] Brill, page 1