serum esrum sreum rseum ersum resum seurm esurm suerm userm eusrm uesrm sruem rsuem surem usrem rusem ursem erusm reusm eursm uersm ruesm uresm sermu esrmu sremu rsemu ersmu resmu semru esmru smeru mseru emsru mesru srmeu rsmeu smreu msreu rmseu mrseu ermsu remsu emrsu mersu rmesu mresu seumr esumr suemr usemr eusmr uesmr semur esmur smeur mseur emsur mesur sumer usmer smuer msuer umser muser eumsr uemsr emusr meusr umesr muesr srume rsume surme usrme rusme ursme srmue rsmue smrue msrue rmsue mrsue sumre usmre smure msure umsre musre rumse urmse rmuse mruse umrse murse erums reums eurms uerms ruems urems ermus remus emrus merus rmeus mreus eumrs uemrs emurs meurs umers muers rumes urmes rmues mrues umres mures
Note: these 'words' (valid or invalid) are all the permutations of the word serum. These words are obtained by scrambling the letters in serum.