flunk lfunk fulnk uflnk lufnk ulfnk flnuk lfnuk fnluk nfluk lnfuk nlfuk funlk ufnlk fnulk nfulk unflk nuflk lunfk ulnfk lnufk nlufk unlfk nulfk flukn lfukn fulkn uflkn lufkn ulfkn flkun lfkun fklun kflun lkfun klfun fukln ufkln fkuln kfuln ukfln kufln lukfn ulkfn lkufn klufn uklfn kulfn flnku lfnku fnlku nflku lnfku nlfku flknu lfknu fklnu kflnu lkfnu klfnu fnklu nfklu fknlu kfnlu nkflu knflu lnkfu nlkfu lknfu klnfu nklfu knlfu funkl ufnkl fnukl nfukl unfkl nufkl fuknl ufknl fkunl kfunl ukfnl kufnl fnkul nfkul fknul kfnul nkful knful unkfl nukfl uknfl kunfl nkufl knufl lunkf ulnkf lnukf nlukf unlkf nulkf luknf ulknf lkunf klunf uklnf kulnf lnkuf nlkuf lknuf klnuf nkluf knluf unklf nuklf uknlf kunlf nkulf knulf
Note: these 'words' (valid or invalid) are all the permutations of the word flunk. These words are obtained by scrambling the letters in flunk.