1. in a manner that astonishes or confuses someone greatly; in a way that leaves someone speechless or bewildered
Usage: informal; formed from the adjective 'dumbfounding' (present participle of 'dumbfound')

Examples

• The magician's trick was dumbfoundingly clever, leaving the entire audience in stunned silence.
• She dumbfoundingly announced that she was quitting her job to become a professional dancer.
• The test results were dumbfoundingly difficult; even the top students struggled.
• He spoke dumbfoundingly fast, making it nearly impossible to understand what he was saying.
• The price of the house was dumbfoundingly high for such a small property.
• She dumbfoundingly admitted that she had never read a single book in her life.