Source : Webster's Revised Unabridged Dictionary (1913)

Commutative \Com*mut"a*tive\, a. [CF. F. commutatif.]
   Relative to exchange; interchangeable; reciprocal. --
   {Com*mut"a*tive"ly}, adv.

         Rich traders, from their success, are presumed . . . to
         have cultivated an habitual regard to commutative
         justice.                                 --Burke.

Source : WordNet®

commutative
     adj : of a binary operation; independent of order; as in e.g. "a x
           b = b x a"