When it comes to describing flavors, "sour" is a common term that can be used to describe anything from citrus fruits to fermented foods. However, if you're seeking to broaden your vocabulary, there are plenty of synonyms that can be used in place of "sour". For example, you could describe a flavor as tart, tangy, acidic, pungent, acerbic, or sharp. Other synonyms for sour include bitter, astringent, biting, and acidic. Depending on the context, some of these words may be more appropriate than others, but they all describe a similar flavor profile. Experiment with using different synonyms for sour to add depth and nuance to your writing.