The phrase "sum up" means to give a brief overview of something or to provide a conclusion. Some synonyms for "sum up" include "recap", "summarize", "conclude", "synthesize", "summarily", "boil down", "outline", "restate", and "summarize briefly". Using these words can help one express their thoughts more effectively and efficiently. Whether giving a speech, writing an essay, or leading a meeting, it's important to be able to concisely convey the key points. By using different synonyms for "sum up", one can avoid repetition and add variety to their language.