Astonishing means so surprising or impressive that it's hard to believe. When something is astonishing, it stops you in your tracks and makes you think, “Wait, did that really just happen?”

A gymnast might perform an astonishing routine, flipping and twisting in ways that seem to defy gravity. A scientist might make an astonishing discovery that changes how we understand the universe. When you open a book expecting an ordinary story and find yourself completely captivated by an astonishing plot twist, that's the word at work.

Something astonishing doesn't just impress you. It genuinely surprises you, often because it exceeds what you thought was possible. An excellent test score might make you proud, but an astonishing score would be one so high it surprises even you.

You might also hear people use astonished to describe how they feel: “I was astonished when my quiet classmate turned out to be an incredible singer.” The word suggests that sense of being caught off guard by something remarkable.