There are various synonyms for the phrase "be one up on." Some of the commonly used ones include "be ahead of," "be superior to," "have an advantage over," "outdo," "outsmart," "outpace," "outstrip," "surpass," "outwit," and "excel." These synonyms are often used to describe situations where one person or team has an advantage over another in a competitive environment. The use of synonyms not only helps to diversify the language but also enhances the clarity of communication. Choosing the right synonym depending on the context can help to convey the intended message more appropriately.