jack ajck jcak cjak acjk cajk jakc ajkc jkac kjac akjc kajc jcka cjka jkca kjca ckja kcja ackj cakj akcj kacj ckaj kcaj
Note: these 'words' (valid or invalid) are all the permutations of the word jack. These words are obtained by scrambling the letters in jack.