urban ruban ubran buran rbuan bruan urabn ruabn uarbn aurbn raubn arubn ubarn buarn uabrn aubrn baurn aburn rbaun braun rabun arbun barun abrun urbna rubna ubrna burna rbuna bruna urnba runba unrba nurba rnuba nruba ubnra bunra unbra nubra bnura nbura rbnua brnua rnbua nrbua bnrua nbrua uranb ruanb uarnb aurnb raunb arunb urnab runab unrab nurab rnuab nruab uanrb aunrb unarb nuarb anurb naurb ranub arnub rnaub nraub anrub narub ubanr buanr uabnr aubnr baunr abunr ubnar bunar unbar nubar bnuar nbuar uanbr aunbr unabr nuabr anubr naubr banur abnur bnaur nbaur anbur nabur rbanu branu rabnu arbnu barnu abrnu rbnau brnau rnbau nrbau bnrau nbrau ranbu arnbu rnabu nrabu anrbu narbu banru abnru bnaru nbaru anbru nabru
Note: these 'words' (valid or invalid) are all the permutations of the word urban. These words are obtained by scrambling the letters in urban.