Source : Webster's Revised Unabridged Dictionary (1913)

Nonplus \Non"plus\, n. [L. non not + plus more, further. See
   {Plural}.]
   A state or condition which daffles reason or confounds
   judgment; insuperable difficalty; inability to proceed or
   decide; puzzle; quandary.

         Both of them are a perfect nonplus and baffle to all
         human understanding.                     --South.

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®

nonplus
     v : be a mystery or bewildering to; "This beats me!"; "Got me--I
         don't know the answer!"; "a vexing problem"; "This
         question really stuck me" [syn: {perplex}, {vex}, {stick},
          {get}, {puzzle}, {mystify}, {baffle}, {beat}, {pose}, {bewilder},
          {flummox}, {stupefy}, {gravel}, {amaze}, {dumbfound}]
     [also: {nonplussing}, {nonplusses}, {nonplussed}]