serifs esrifs sreifs rseifs ersifs resifs seirfs esirfs sierfs iserfs eisrfs iesrfs sriefs rsiefs sirefs isrefs risefs irsefs erisfs reisfs eirsfs iersfs riesfs iresfs serfis esrfis srefis rsefis ersfis resfis sefris esfris sferis fseris efsris fesris srfeis rsfeis sfreis fsreis rfseis frseis erfsis refsis efrsis fersis rfesis fresis seifrs esifrs siefrs isefrs eisfrs iesfrs sefirs esfirs sfeirs fseirs efsirs fesirs sifers isfers sfiers fsiers ifsers fisers eifsrs iefsrs efisrs feisrs ifesrs fiesrs srifes rsifes sirfes isrfes risfes irsfes srfies rsfies sfries fsries rfsies frsies sifres isfres sfires fsires ifsres fisres rifses irfses rfises frises ifrses firses erifss reifss eirfss ierfss riefss irefss erfiss refiss efriss feriss rfeiss freiss eifrss iefrss efirss feirss iferss fierss rifess irfess rfiess friess ifress firess serisf esrisf sreisf rseisf ersisf resisf seirsf esirsf siersf isersf eisrsf iesrsf sriesf rsiesf siresf isresf risesf irsesf erissf reissf eirssf ierssf riessf iressf sersif esrsif sresif rsesif erssif ressif sesrif essrif sserif sserif essrif sesrif srseif rsseif ssreif ssreif rsseif srseif erssif ressif esrsif sersif rsesif sresif seisrf esisrf siesrf isesrf eissrf iessrf sesirf essirf sseirf sseirf essirf sesirf siserf isserf ssierf ssierf isserf siserf eissrf iessrf esisrf seisrf isesrf siesrf srisef rsisef sirsef isrsef rissef irssef srsief rssief ssrief ssrief rssief srsief sisref issref ssiref ssiref issref sisref rissef irssef rsisef srisef isrsef sirsef erissf reissf eirssf ierssf riessf iressf ersisf resisf esrisf serisf rseisf sreisf eisrsf iesrsf esirsf seirsf isersf siersf risesf irsesf rsiesf sriesf isresf siresf serfsi esrfsi srefsi rsefsi ersfsi resfsi sefrsi esfrsi sfersi fsersi efsrsi fesrsi srfesi rsfesi sfresi fsresi rfsesi frsesi erfssi refssi efrssi ferssi rfessi fressi sersfi esrsfi sresfi rsesfi erssfi ressfi sesrfi essrfi sserfi sserfi essrfi sesrfi srsefi rssefi ssrefi ssrefi rssefi srsefi erssfi ressfi esrsfi sersfi rsesfi sresfi sefsri esfsri sfesri fsesri efssri fessri sesfri essfri ssefri ssefri essfri sesfri sfseri fsseri ssferi ssferi fsseri sfseri efssri fessri esfsri sefsri fsesri sfesri srfsei rsfsei sfrsei fsrsei rfssei frssei srsfei rssfei ssrfei ssrfei rssfei srsfei sfsrei fssrei ssfrei ssfrei fssrei sfsrei rfssei frssei rsfsei srfsei fsrsei sfrsei erfssi refssi efrssi ferssi rfessi fressi ersfsi resfsi esrfsi serfsi rsefsi srefsi efsrsi fesrsi esfrsi sefrsi fsersi sfersi rfsesi frsesi rsfesi srfesi fsresi sfresi seifsr esifsr siefsr isefsr eisfsr iesfsr sefisr esfisr sfeisr fseisr efsisr fesisr sifesr isfesr sfiesr fsiesr ifsesr fisesr eifssr iefssr efissr feissr ifessr fiessr seisfr esisfr siesfr isesfr eissfr iessfr sesifr essifr sseifr sseifr essifr sesifr sisefr issefr ssiefr ssiefr issefr sisefr eissfr iessfr esisfr seisfr isesfr siesfr sefsir esfsir sfesir fsesir efssir fessir sesfir essfir ssefir ssefir essfir sesfir sfseir fsseir ssfeir ssfeir fsseir sfseir efssir fessir esfsir sefsir fsesir sfesir sifser isfser sfiser fsiser ifsser fisser sisfer issfer ssifer ssifer issfer sisfer sfsier fssier ssfier ssfier fssier sfsier ifsser fisser isfser sifser fsiser sfiser eifssr iefssr efissr feissr ifessr fiessr eisfsr iesfsr esifsr seifsr isefsr siefsr efsisr fesisr esfisr sefisr fseisr sfeisr ifsesr fisesr isfesr sifesr fsiesr sfiesr srifse rsifse sirfse isrfse risfse irsfse srfise rsfise sfrise fsrise rfsise frsise sifrse isfrse sfirse fsirse ifsrse fisrse rifsse irfsse rfisse frisse ifrsse firsse srisfe rsisfe sirsfe isrsfe rissfe irssfe srsife rssife ssrife ssrife rssife srsife sisrfe issrfe ssirfe ssirfe issrfe sisrfe rissfe irssfe rsisfe srisfe isrsfe sirsfe srfsie rsfsie sfrsie fsrsie rfssie frssie srsfie rssfie ssrfie ssrfie rssfie srsfie sfsrie fssrie ssfrie ssfrie fssrie sfsrie rfssie frssie rsfsie srfsie fsrsie sfrsie sifsre isfsre sfisre fsisre ifssre fissre sisfre issfre ssifre ssifre issfre sisfre sfsire fssire ssfire ssfire fssire sfsire ifssre fissre isfsre sifsre fsisre sfisre rifsse irfsse rfisse frisse ifrsse firsse risfse irsfse rsifse srifse isrfse sirfse rfsise frsise rsfise srfise fsrise sfrise ifsrse fisrse isfrse sifrse fsirse sfirse erifss reifss eirfss ierfss riefss irefss erfiss refiss efriss feriss rfeiss freiss eifrss iefrss efirss feirss iferss fierss rifess irfess rfiess friess ifress firess erisfs reisfs eirsfs iersfs riesfs iresfs ersifs resifs esrifs serifs rseifs sreifs eisrfs iesrfs esirfs seirfs iserfs sierfs risefs irsefs rsiefs sriefs isrefs sirefs erfsis refsis efrsis fersis rfesis fresis ersfis resfis esrfis serfis rsefis srefis efsris fesris esfris sefris fseris sferis rfseis frseis rsfeis srfeis fsreis sfreis eifsrs iefsrs efisrs feisrs ifesrs fiesrs eisfrs iesfrs esifrs seifrs isefrs siefrs efsirs fesirs esfirs sefirs fseirs sfeirs ifsers fisers isfers sifers fsiers sfiers rifses irfses rfises frises ifrses firses risfes irsfes rsifes srifes isrfes sirfes rfsies frsies rsfies srfies fsries sfries ifsres fisres isfres sifres fsires sfires
Note: these 'words' (valid or invalid) are all the permutations of the word serifs. These words are obtained by scrambling the letters in serifs.