Openmouthed is a term that refers to the state of having one's mouth wide open, often in shock or surprise. There are several synonyms for this term that can be used to convey the same meaning. These include agape, aghast, flabbergasted, astounded, thunderstruck, speechless, dumbfounded, and stunned. All of these words express a sense of stunned amazement or disbelief, and are suitable for describing someone's reaction to a surprising or unexpected event. Using these synonyms instead of the more common openmouthed can help to add variety and interest to your writing, and convey a more nuanced sense of emotion.