dumbfound also dumfound
dumb-found / dŭm–found
1. to perplex with amazement; to confound; to shock and leave speechless
It’s not easy to dumbfound a New Yorker.
Taehee Kim, “Just Another Day on the Sidewalks of New York”, ‘Smithsonian Magazine’, May 1997
dumb-found-ed / dŭm–found-ĕd
1. astonished; surprised; amazed
I never cease being dumbfounded by the unbelievable things people believe.
Leo Rosten, 1908 – 1997