Exceedingly is an adverb used to describe something that is done to a great extent or degree. When looking for synonyms, one could use words such as extremely, exceptionally, tremendously, remarkably, and incredibly. These adverbs all convey the same meaning of something being done to a very high level. Other words that can be used as synonyms include immensely, hugely, vastly, and excessively. It's important to choose the correct synonym depending on the context of the sentence. By using different synonyms, a writer can avoid repetition and make their writing more interesting and varied.