The term "lower side" can be replaced by various synonyms depending on the context. For example, if we are talking about the opposite side of the upper side, we can use the term "underside." In the case of a graph or chart, we could use words such as "bottom" or "base" to refer to the lower end of the scale. Alternatively, we can use the word "inferior" to describe something of a lower quality or rank. Some other synonyms include "subordinate," "secondary," and "lesser." Overall, the right synonym depends on the specific situation in which it is used.