The Collaborative International Dictionary of English v.0.48:

Retorsion \Re*tor"sion\, n.
   Same as Retortion.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Retortion \Re*tor"tion\, n. [Cf. F. r['e]torsion. See Retort,
   v. t.]
   1. Act of retorting or throwing back; reflection or turning
      back. [Written also retorsion.]
      [1913 Webster]

            It was, however, necessary to possess some single
            term expressive of this intellectual retortion.
                                                  --Sir W.
                                                  Hamilton.
      [1913 Webster]

   2. (Law) Retaliation. --Wharton.
      [1913 Webster]