Astonishing, meaning breathtaking or amazing, has many synonyms that can be used to add depth and variety to one's writing. One such synonym is astounding, which conveys a sense of shock and surprise. Another word that can be used in place of astonishing is staggering, which indicates that something is so surprising that it may be difficult to comprehend. Other synonyms include remarkable, impressive, awe-inspiring, and incredible. Each of these words can be used to convey a similar meaning to astonishing, but with a slightly different connotation. By using synonyms, writers can add interest and variety to their language and convey the depth of their ideas more effectively.