Part of Speech: Adjective
Synonym(s): stunned, overwhelmed
1. Knowing how smart my daughter is, I was completely dumbfounded when she announced her plans to drop out of school.
2. When I finally had the chance to meet my idol, I was so dumbfounded I couldn't speak
3. Helen, who is never at a loss for words, was dumbfounded when she saw her son’s filthy apartment.