Definition of "quixotic"

Olivier, as you know, was quixotic, and would not permit a secret service and spies.

1911 January 7, G[ilbert] K[eith] Chesterton, “The Sign of the Broken Sword”, in The Innocence of Father Brown, London, New York, N.Y.: Cassell and Company, published 1911

The message is not subliminal. […] Characters aren’t just quixotic, they cite Cervantes to one another.

2012 June 21, Alessandra Stanley, “So Sayeth the Anchorman”, in The New York Times‎

The war triggered in [Miguel de] Unamuno the realization that, in hopeless times, quixotic lunacy could save people from the paralysis that often accompanies defeatism.

2017 May 29, Mariana Alessandri, “In Praise of Lost Causes”, in The New York Times‎

In the digital age, building a new library filled with old-fashioned printed books seems idealistic, almost quixotic.

2022 April 17, Stephen Burgen, “Barcelona honours Gabriel García Márquez with new library”, in The Observer‎

The cultural quixotics attribute the change to inscrutable "cultural factors," which is tantamount to abandoning altogether the search for explanation.

1975, Michael B. Schiffer, John H. House, The Cache River Archeological Project, page 179