orbku robku obrku borku rboku broku orkbu rokbu okrbu korbu rkobu krobu obkru bokru okbru kobru bkoru kboru rbkou brkou rkbou krbou bkrou kbrou orbuk robuk obruk boruk rbouk brouk orubk roubk ourbk uorbk ruobk urobk oburk bourk oubrk uobrk buork ubork rbuok bruok rubok urbok burok ubrok orkub rokub okrub korub rkoub kroub orukb roukb ourkb uorkb ruokb urokb okurb kourb oukrb uokrb kuorb ukorb rkuob kruob rukob urkob kurob ukrob obkur bokur okbur kobur bkour kbour obukr boukr oubkr uobkr buokr ubokr okubr koubr oukbr uokbr kuobr ukobr bkuor kbuor bukor ubkor kubor ukbor rbkuo brkuo rkbuo krbuo bkruo kbruo rbuko bruko rubko urbko burko ubrko rkubo krubo rukbo urkbo kurbo ukrbo bkuro kburo bukro ubkro kubro ukbro
Note: these 'words' (valid or invalid) are all the permutations of the word orbku. These words are obtained by scrambling the letters in orbku.