retro ertro rtero trero etrro terro rerto errto rreto rreto errto rerto rtreo trreo rrteo rrteo trreo rtreo etrro terro ertro retro trero rtero retor ertor rteor treor etror teror reotr erotr roetr oretr eortr oertr rtoer troer roter orter torer otrer etorr teorr eotrr oetrr toerr oterr rerot errot rreot rreot errot rerot reort erort roert orert eorrt oerrt rroet rroet roret orret roret orret erort reort eorrt oerrt roert orert rtroe trroe rrtoe rrtoe trroe rtroe rtore trore rotre ortre torre otrre rrote rrote rorte orrte rorte orrte trore rtore torre otrre rotre ortre etror teror ertor retor treor rteor etorr teorr eotrr oetrr toerr oterr erotr reotr eortr oertr roetr oretr troer rtoer torer otrer roter orter
Note: these 'words' (valid or invalid) are all the permutations of the word retro. These words are obtained by scrambling the letters in retro.