umbra mubra ubmra bumra mbura bmura umrba murba urmba rumba mruba rmuba ubrma burma urbma rubma bruma rbuma mbrua bmrua mrbua rmbua brmua rbmua umbar mubar ubmar bumar mbuar bmuar umabr muabr uambr aumbr maubr amubr ubamr buamr uabmr aubmr baumr abumr mbaur bmaur mabur ambur bamur abmur umrab murab urmab rumab mruab rmuab umarb muarb uamrb aumrb maurb amurb uramb ruamb uarmb aurmb raumb arumb mraub rmaub marub amrub ramub armub ubram buram urbam rubam bruam rbuam ubarm buarm uabrm aubrm baurm aburm urabm ruabm uarbm aurbm raubm arubm braum rbaum barum abrum rabum arbum mbrau bmrau mrbau rmbau brmau rbmau mbaru bmaru mabru ambru bamru abmru mrabu rmabu marbu amrbu rambu armbu bramu rbamu barmu abrmu rabmu arbmu
Note: these 'words' (valid or invalid) are all the permutations of the word umbra. These words are obtained by scrambling the letters in umbra.