Definition of "mitred"

Our Fathers must hide themselves rather like robbers who chuse a leader, than godly priests who elect a mitred Abbot. […] And mark me, brother! not in the proudest days of the mitred Abbey, was a Superior ever chosen, whom his office shall so much honour, as he shall be honoured, who now takes it upon him in these days of tribulation.

1820, [Walter Scott], chapter XIII, in The Abbot. […], volume I, Edinburgh: […] [James Ballantyne & Co.] for Longman, Hurst, Rees, Orme, and Brown, […]; and for Archibald Constable and Company, and John Ballantyne, […], pages 275–276

Mitred emissaries also passed from Gregory to the Emperor, summoning him to attend the diet within a time by which no one unwafted by wings or steam could have reached the place […]

1871, Elizabeth Missing Sewell, European History, page 193

Their leaves were green when the Abbey rose in splendour, and mitred abbots walked in their shadow.

1904, George Hodges, Fountains Abbey, the story of a mediaeval monastery, page 2

Again I bestride the mitred, leather-winged steed.

1981, Gene Wolfe, chapter VIII, in The Claw of the Conciliator (The Book of the New Sun; 2), New York: Timescape, page 71