Époustouflé

Flabbergasted.  Astounded.

I’m cheating here because Epoustouflé entered my vocabulary a couple of months ago, but it’s such a great word, it needs to be shared!

For best effect, you have to pronounce it in a certain way : Ay-POOS-too-flay!! And waving your hands around a bit helps give it a bit more emphasis, too.