1. present participle of dumfound; causing someone to be bewildered, confused, or astonished
Usage: often used in progressive or continuous forms

1. extremely confusing or astonishing; leaving someone speechless or unable to respond
Usage: informal; chiefly British

Examples

• The magician's trick was absolutely dumfoundering—no one could figure out how he did it.
• She found his explanation dumfoundering rather than helpful.
• The sudden announcement was dumfoundering to everyone in the room.
• He stood there, dumfoundering at the unexpected news.
• The complexity of the problem proved dumfoundering for most students.
• They were dumfoundering the audience with their bizarre performance art.