Definition of "nonplussed"

[N]ote the honeſt Quaker vvas nonpluſſed, and greatly ſurprized at that Queſtion.

1724, [Daniel Defoe], The Fortunate Mistress; […], London: […] E. Applebee, […], published 1740, page 277

I could not discern what she meant, and I would not ask her: I was nonplussed.

1853 January, Currer Bell [pseudonym; Charlotte Brontë], “A Burial”, in Villette. […], volume III, London: Smith, Elder & Co., […], page 285

For the nonce he was rather nonplussed but inasmuch as the duty plainly devolved upon him to take some measures on the subject he pondered suitable ways and means during which Stephen repeatedly yawned.

1922 February, James Joyce, “[Episode 16: Eumaeus]”, in Ulysses, Paris: Shakespeare and Company, […], part III [Nostos], page 569

You couldn’t have told it from my manner, but I was feeling more than a bit nonplussed. The spectacle before me was enough to nonplus anyone.

1934 October 5, P[elham] G[renville] Wodehouse, chapter II, in Right Ho, Jeeves, London: Herbert Jenkins […], page 24

In the opposite direction the allowance of 103 min. for the 83.8 miles from Waterloo to Salisbury, which has remained untouched since the worst period in the war, when it included a Woking stop that long since has been excised, was another timing that left drivers completely nonplussed at times as to how to fill it out.

1949 July and August, Cecil J. Allen, “British Locomotive Practice and Performance”, in Railway Magazine, page 257

"I regard Dean [W. P.] Baddeley's gambling activities with embarrassment and dismay," said Anglican dean of Melbourne S. Barton Babbage. […] The Rev. Baddeley remained nonplussed. "I don't intend to make a habit of going to the races but I feel clergymen should mix as our Lord did with all walks of life," Dr. Baddeley said.This is the earliest occurrence of this sense of the word recorded by the Oxford English Dictionary.

1960 August 2, “Cleric’s error was to win his wagers”, in Oakland Tribune, home edition, volume CLXXIII, number 33, Oakland, Calif.: Oakland Tribune, page E7, column 6

And while many of us might be a little taken aback if Mom showed up at our offices, Secrist is utterly nonplussed, even happy about it.

2002 April 14, Debra Pickett, “Sunday lunch with”, in Chicago Sun-Times, Chicago, Ill.: Chicago Public Media, page 24

One cannot help but wonder how the unnecessary death of 10 men sat on [John Charles] Fremont's conscience. From all appearances, he seemed nonplussed and never was remorseful or contrite.

2003 September, Gerald F. Kreyche, “John Charles Fremont and the Exploration of the American West”, in USA Today‎, volume 132, number 2700, New York, N.Y.: Society for the Advancement of Education, archived from the original on 2023-03-13, pages 52–57

My screams woke everyone on the boat the first night when a large bat flapped up against the screen door to our small cabin, with its foam double beds. My brother-in-law, Mike, was nonplussed: "Why would you get excited over a little bug like that?"

2004 June, Shannon Thompson, “Houseboating on California’s Shasta Lake”, in Sunset‎, volume 212, number 6, Oakland, Calif.: Sunset Publishing, published 2 September 2004 (online), archived from the original on 2022-08-12, page 140

The lions in question were nonplussed. "They just stuck their noses into the wind, looked around and slumped down again into the grass," the now 73-year-old [Jonathan Scott] recalls.

2022 August 14, Joe Shute, “The rise and fall of the pride that inspired the Lion King”, in Chris Evans, editor, The Daily Telegraph‎, London: Telegraph Media Group, archived from the original on 2022-11-30