turbk utrbk trubk rtubk urtbk rutbk tubrk utbrk tburk bturk ubtrk butrk trbuk rtbuk tbruk btruk rbtuk brtuk urbtk rubtk ubrtk burtk rbutk brutk turkb utrkb trukb rtukb urtkb rutkb tukrb utkrb tkurb kturb uktrb kutrb trkub rtkub tkrub ktrub rktub krtub urktb ruktb ukrtb kurtb rkutb krutb tubkr utbkr tbukr btukr ubtkr butkr tukbr utkbr tkubr ktubr uktbr kutbr tbkur btkur tkbur ktbur bktur kbtur ubktr buktr ukbtr kubtr bkutr kbutr trbku rtbku tbrku btrku rbtku brtku trkbu rtkbu tkrbu ktrbu rktbu krtbu tbkru btkru tkbru ktbru bktru kbtru rbktu brktu rkbtu krbtu bkrtu kbrtu urbkt rubkt ubrkt burkt rbukt brukt urkbt rukbt ukrbt kurbt rkubt krubt ubkrt bukrt ukbrt kubrt bkurt kburt rbkut brkut rkbut krbut bkrut kbrut
Note: these 'words' (valid or invalid) are all the permutations of the word turbk. These words are obtained by scrambling the letters in turbk.