mtbot tmbot mbtot bmtot tbmot btmot mtobt tmobt motbt omtbt tombt otmbt mbott bmott mobtt ombtt bomtt obmtt tbomt btomt tobmt otbmt botmt obtmt mtbto tmbto mbtto bmtto tbmto btmto mttbo tmtbo mttbo tmtbo ttmbo ttmbo mbtto bmtto mtbto tmbto btmto tbmto tbtmo bttmo ttbmo ttbmo bttmo tbtmo mtotb tmotb mottb omttb tomtb otmtb mttob tmtob mttob tmtob ttmob ttmob mottb omttb mtotb tmotb otmtb tomtb totmb ottmb ttomb ttomb ottmb totmb mbott bmott mobtt ombtt bomtt obmtt mbtot bmtot mtbot tmbot btmot tbmot motbt omtbt mtobt tmobt otmbt tombt botmt obtmt btomt tbomt otbmt tobmt tbotm btotm tobtm otbtm bottm obttm tbtom bttom ttbom ttbom bttom tbtom totbm ottbm ttobm ttobm ottbm totbm bottm obttm btotm tbotm otbtm tobtm
Note: these 'words' (valid or invalid) are all the permutations of the word mtbot. These words are obtained by scrambling the letters in mtbot.