Source : Webster's Revised Unabridged Dictionary (1913)

Nonplus \Non"plus`\, v. t. [imp. & p. p. {Nonplused}or
   {Nonplussed}; p. pr. & vb. n. {Nonplusing} or {Nonplussing}.]
   To puzzle; to confound; to perplex; to cause to stop by
   embarrassment.

         He has been nonplused by Mr. Dry's desiring him to tell
         what it was that he endeavored to prove. --Spectator.

Source : WordNet®

nonplused
     adj : filled with bewilderment; "at a loss to understand those
           remarks"; "puzzled that she left without saying
           goodbye" [syn: {at a loss(p)}, {nonplussed}, {puzzled}]