The transposability of a word can be defined as the ease with which its letters can be rearranged to form another word. This can be quanitified in two ways -- the number of different words into which the letters can be rearranged, and their rarity. As demonstrated by Dmitri Borgmann in "Elementary Transpositions" in the August 1978 Word Ways, it is usually possible to transpose a word if one is willing to stretch the concept of a "word" to its outer limits (and beyond).
Francis, Darryl and Eckler, A. Ross
Word Ways: Vol. 11
, Article 3.
Available at: http://digitalcommons.butler.edu/wordways/vol11/iss4/3