"Ur-" is a prefix that can be added to various words to indicate the primitive or original form of something. However, there are a few synonyms that can be used in its place, depending on the context. For example, one synonym for "ur-" could be the word "proto-", which denotes the initial stage or earliest form of something. Another possible synonym could be "primordial", which refers to the very first or original state of something. Additionally, "archaic" or "ancient" can also be used as synonyms for "ur-" when referring to something that is extremely old or outdated. Overall, there are many possible alternatives to the prefix "ur-", depending on the specific meaning and usage of the word.