I said to him, "How do you know the word flabbergasted?"
He said, "From you guys."
So I asked him if he knew what it meant, and he said, "Really surprised and sort of scared." So his definition wasn't 100% dead-on, but pretty good for a 4 year-old, I thought!
Later on he used it again when he said, "I'm going to flabbergast Brad when I give him this birthday card."
I have a feeling flabbergasted is a word we'll suddenly be hearing a lot of.