Definition of "nonplus"

nonplus

/nɒnˈplʌs/

noun
plural nonpluses
1. A state of bewilderment or perplexity.
  Quotations
  [A]ltering Vaudemont, to Vallemontanus, and metamorphosing them, by suting them to the Græcian or Latin tongue, we know not what to make of them, and are often at a non-plus.
  1603, Michel de Montaigne, chapter XLVI, in John Florio, transl., The Essayes […], book I, London: […] Val[entine] Simmes for Edward Blount […]
  Both of them are a perfect non-plus and baffle to all human understanding.
  1692–1717, Robert South, Twelve Sermons Preached upon Several Occasions, 6th edition, volumes (please specify |volume=I to VI), London: […] J[ames] Bettenham, for Jonah Bowyer, […], published 1727
  I believe they'd soon be put to a non-plus — You'd be quite too much for them, I'm sure.
  1792, Charlotte Smith, Desmond, Broadview, published 2001, page 81
verb
third-person singular simple present nonplusses or nonpluses, present participle nonplussing or nonplusing, simple past and past participle nonplussed or nonplused
1. (transitive) To bewilder or perplex (someone); to confound, to flummox.
  Quotations
  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