The Collaborative International Dictionary of English v.0.48:

Commute \Com*mute"\ (k[o^]m*m[=u]t"), v. t. [imp. & p. p.
   Commuted; p. pr. & vb. n. Commuting.] [L. commutare,
   -mutatum; com- + mutare to change. See Mutation.]
   1. To exchange; to put or substitute something else in place
      of, as a smaller penalty, obligation, or payment, for a
      greater, or a single thing for an aggregate; hence, to
      lessen; to diminish; as, to commute a sentence of death to
      one of imprisonment for life; to commute tithes; to
      commute charges for fares.
      [1913 Webster]

            The sounds water and fire, being once annexed to
            those two elements, it was certainly more natural to
            call beings participating of the first "watery", and
            the last "fiery", than to commute the terms, and
            call them by the reverse.             --J. Harris
      [1913 Webster]

            The utmost that could be obtained was that her
            sentence should be commuted from burning to
            beheading.                            --Macaulay.
      [1913 Webster]