An ordering of Permutations in which each two adjacent permutations differ by the Transposition of two elements. For the permutations of there are two listings which are in transposition order. One is 123, 132, 312, 321, 231, 213, and the other is 123, 321, 312, 213, 231, 132.
See also Lexicographic Order, Permutation
References
Ruskey, F. ``Information on Combinations of a Set.''
http://sue.csc.uvic.ca/~cos/inf/comb/CombinationsInfo.html.