Things that might astonish you: the discovery of life on another planet, a death-defying performance, and the number of dinosaurs a six-year old child can name. To astonish is to amaze and astound.
Remember that astonish means more than surprised. It carries with it a feeling of being truly impressed. Astonish derives from the Latin tonare 'thunder.' When you are astonished, you're thunderstruck. If you plan to astonish someone, you might say before hand, "Wait until you see this. It's going to knock your socks off."