1. 
[syn: dumbfounded, dumfounded, flabbergasted, stupefied, thunderstruck, dumbstruck, dumbstricken]
The Collaborative International Dictionary of English v.0.48:
dumfounded \dumfounded\ adj.
   same as dumbfounded.
   Syn: amazed, astonied, astonished, astounded, flabbergasted,
        stunned, stupefied, thunderstruck.
        [WordNet 1.5]
The Collaborative International Dictionary of English v.0.48:
Dumfound \Dum"found`\, v. t. [imp. & p. p. Dumfounded; p. pr.
   & vb. n. Dumfounding.]
   To strike dumb; to confuse with astonishment. [Written also
   dumbfound.] --Spectator.
   [1913 Webster]
WordNet (r) 3.0 (2006):
dumfounded
    adj 1: as if struck dumb with astonishment and surprise; "a
           circle of policement stood dumbfounded by her denial of
           having seen the accident"; "the flabbergasted aldermen
           were speechless"; "was thunderstruck by the news of his
           promotion" [syn: dumbfounded, dumfounded,
           flabbergasted, stupefied, thunderstruck,
           dumbstruck, dumbstricken]