Jaw-dropper is a colloquial term used to describe something that is amazing, astonishing, or impressive. However, there are several other synonyms available that can be used in its place to describe something that leaves us speechless. Some possible alternatives include 'showstopper', 'eyebrow-raiser', 'spectacle', 'miracle', 'stunning', 'breathtaking', 'awe-inspiring', 'mesmerizing', 'splendid', 'impressive', 'mind-blowing', 'mind-boggling', 'phenomenal', 'unbelievable', 'outstanding', and 'marvelous'. No matter which of these synonyms you choose to use, they all convey the same sense of awe and amazement that leaves an indelible impression on the viewer.