• (British) IPA: /nɒnˈplʌst/
• (GA) IPA: /nɑnˈplʌst/

nonplussed

1. Bewildered; unsure how to respond or act. [from 17th c.]
   • 1724, Daniel Defoe, Roxana: The Fortunate Mistress:

     Note, the honest Quaker was nonplussed, and greatly surprised at that question.

   • 1922 February, James Joyce, “[Episode 16]”, in Ulysses, Paris: Shakespeare & Co.; Sylvia Beach, OCLC 560090630 ↗; republished London: Published for the Egoist Press, London by John Rodker, Paris, October 1922, OCLC 2297483 ↗:

     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.

   • 2000, Marcia Miller & Martin Lee, Vocabulary, Word of the Day

     "Dad was so nonplussed by the new VCR that he gave up and asked Mom to set it for him".

2. (proscribed, US, informal) Unfazed, unaffected, or unimpressed. [from 20th c.]

• (bewildered) perplexed, vexed, thwarted, frustrated, foiled, confounded

• French: interloqué, déconcerté, perplexe
• German: verblüfft
• Italian: perplesso
• Portuguese: desconcertado, perplexo
• Russian: расте́рянный
• Spanish: perplejo

• French: imperturbable, détaché
• German: unbeeindruckt

1. Simple past tense and past participle of nonplus