truck rtuck turck utrck rutck urtck trcuk rtcuk tcruk ctruk rctuk crtuk tucrk utcrk tcurk cturk uctrk cutrk ructk urctk rcutk crutk ucrtk curtk trukc rtukc turkc utrkc rutkc urtkc trkuc rtkuc tkruc ktruc rktuc krtuc tukrc utkrc tkurc kturc uktrc kutrc ruktc urktc rkutc krutc ukrtc kurtc trcku rtcku tcrku ctrku rctku crtku trkcu rtkcu tkrcu ktrcu rktcu krtcu tckru ctkru tkcru ktcru cktru kctru rcktu crktu rkctu krctu ckrtu kcrtu tuckr utckr tcukr ctukr uctkr cutkr tukcr utkcr tkucr ktucr uktcr kutcr tckur ctkur tkcur ktcur cktur kctur ucktr cuktr ukctr kuctr ckutr kcutr ruckt urckt rcukt crukt ucrkt curkt rukct urkct rkuct kruct ukrct kurct rckut crkut rkcut krcut ckrut kcrut uckrt cukrt ukcrt kucrt ckurt kcurt
Note: these 'words' (valid or invalid) are all the permutations of the word truck. These words are obtained by scrambling the letters in truck.