The word "downsideup" is a unique and uncommon word, so there are limited synonyms available to describe it. However, some potential synonyms for "downsideup" could include "upside-down," "inverted," "reversed," "contrarian," or "opposite." Depending on the context, other words such as "abnormal," "dysfunctional," or "unconventional" may also be appropriate. Overall, when searching for synonyms for "downsideup," it is important to consider the intended meaning and usage of the word in order to select the most appropriate alternative.