nsubd snubd nusbd unsbd sunbd usnbd nsbud snbud nbsud bnsud sbnud bsnud nubsd unbsd nbusd bnusd ubnsd bunsd subnd usbnd sbund bsund ubsnd busnd nsudb snudb nusdb unsdb sundb usndb nsdub sndub ndsub dnsub sdnub dsnub nudsb undsb ndusb dnusb udnsb dunsb sudnb usdnb sdunb dsunb udsnb dusnb nsbdu snbdu nbsdu bnsdu sbndu bsndu nsdbu sndbu ndsbu dnsbu sdnbu dsnbu nbdsu bndsu ndbsu dnbsu bdnsu dbnsu sbdnu bsdnu sdbnu dsbnu bdsnu dbsnu nubds unbds nbuds bnuds ubnds bunds nudbs undbs ndubs dnubs udnbs dunbs nbdus bndus ndbus dnbus bdnus dbnus ubdns budns udbns dubns bduns dbuns subdn usbdn sbudn bsudn ubsdn busdn sudbn usdbn sdubn dsubn udsbn dusbn sbdun bsdun sdbun dsbun bdsun dbsun ubdsn budsn udbsn dubsn bdusn dbusn
Note: these 'words' (valid or invalid) are all the permutations of the word nsubd. These words are obtained by scrambling the letters in nsubd.