Dumbfounded means so surprised or shocked that you can't speak or think clearly. When you're dumbfounded, your mind goes blank and your mouth hangs open because something has caught you completely off guard.

Picture opening your locker to find it filled with balloons, or having your teacher announce that your class won a pizza party you didn't even know you'd entered. That frozen moment when you can't quite process what's happening? That's being dumbfounded.

When you're dumbfounded, you're struck speechless by surprise or confusion. You might stand there dumbfounded when your best friend reveals they're moving to another state, or when you discover your science project won first place at the fair.

Being dumbfounded usually passes quickly once your brain catches up with what just happened, but in that moment, you're totally stunned. It's stronger than just being surprised: being dumbfounded means the surprise is so complete that it short-circuits your ability to respond.