The phrase "all at once" can often be replaced with synonyms that convey the same meaning. Some examples of synonyms for "all at once" include "simultaneously", "concurrently", "in unison", "at the same time", and "in tandem". Using such synonyms can add variety and depth to one's writing, while avoiding repetition. Additionally, choosing the most fitting synonym can emphasize different aspects of the situation being described. For instance, "simultaneously" might be used to emphasize equal importance, whereas "in unison" might emphasize unity or synchronization. Knowing a variety of synonyms for common phrases such as "all at once" can bring precision and impact to one's writing.