mixu imxu mxiu xmiu ixmu ximu miux imux muix umix iumx uimx mxui xmui muxi umxi xumi uxmi ixum xium iuxm uixm xuim uxim
Note: these 'words' (valid or invalid) are all the permutations of the word mixu. These words are obtained by scrambling the letters in mixu.