Definition of "unaccustomed"

[…] I again conveyed his Key into his Pocket, and counterfeiting Sleep, tho’ I never once cloſed my Eyes, lay in Bed till after he aroſe and went to Prayers, an Exerciſe to which I had long been unaccuſtomed.

1749, Henry Fielding, “In which the Man of the Hill begins to relate his History”, in The History of Tom Jones, a Foundling, volume III, London: A[ndrew] Millar, […], book VIII, page 244

“Do Veniam,” said his Superior; and the old man seized, with a trembling hand, a beverage to which he had been long unaccustomed, drained the cup with protracted delight, as if dwelling on the flavour and perfume, and set it down with a melancholy smile and shake of the head, as if bidding adieu in future to such delicious potations.

1820, [Walter Scott], chapter XV, 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 345–346

He stood transfixed before the unaccustomed view of London at night time, a vast panorama which reminded him […] of some wood engravings far off and magical, in a printshop in his childhood.

1963, Margery Allingham, “Foreword: The Turk Street Mile”, in The China Governess: A Mystery, London: Chatto & Windus, page 11

Guerrilla warfare opens a field of activity for every local capacity, forces the enemy into an unaccustomed method of battle, avoids the evil consequences of a great defeat, secures the national war from the risk of treason, and has the advantage of not confining it within any defined and determinate basis of operations.

1909, James Harvey Robinson, Charles Austin Beard, Readings in Modern European History: Europe since the Congress of Vienna, page 118

I have taken the unaccustomed step of forwarding this letter to the FCC and a number of gay media, essentially because of Mr. Doyle's arrogant attitude concerning this matter.

1984 April 14, Jonathan Handel, “Fruits on Air”, in Gay Community News, page 4