Permutation :: Permutation (n.) The act of permuting; exchange of the thing for another; mutual transference; interchange.
Permutation :: Permutation (n.) The arrangement of any determinate number of things, as units, objects, letters, etc., in all possible orders, one after the other; -- called also alternation. Cf. Combination, n., 4..
Permutation :: Permutation (n.) Any one of such possible arrangements.