xfib fxib xifb ixfb fixb ifxb xfbi fxbi xbfi bxfi fbxi bfxi xibf ixbf xbif bxif ibxf bixf fibx ifbx fbix bfix ibfx bifx
Note: these 'words' (valid or invalid) are all the permutations of the word xfib. These words are obtained by scrambling the letters in xfib.