dumb·found /ˌdʌmˈfaʊnd, ˈdʌmˌ/
  (v.)使人惙然失聲;使發楞
  Dum·found v. t. [imp. & p. p. Dumfounded; p. pr. & vb. n. Dumfounding.] To strike dumb; to confuse with astonishment. [Written also dumbfound.]
  ◄ ►
  dumbfound
       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, nonplus, gravel, amaze]