When it comes to expressing surprise or shock, there are many synonyms for the phrase "open mouth." Some of the most common alternatives to "open mouth" include "jaw dropped," "mouth agape," "gaping mouth," and "mouth wide open." Other phrases that may be used to describe this particular expression include "speechless," "astonished," and "flabbergasted." These synonyms can help to add variety and nuance to your writing, helping to convey emotions in a more precise and vivid way. Regardless of which term you choose, though, the important thing is to use language that truly captures the impact of the moment.