dumbfounding

dumb·found

also dum·found (dŭm′found′)tr.v. dumb·found·ed, dumb·found·ing, dumb·founds also dum·found·ed or dum·found·ing or dum·founds To fill with astonishment and perplexity; confound. See Synonyms at surprise.

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[dumb + (con)found.]

Thesaurus

Adj.

1.

dumbfounding - bewildering or striking dumb with wonderastounding, dumfoundingincredible, unbelievable - beyond belief or understanding; "at incredible speed"; "the book's plot is simply incredible"