What is "retorsion"

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.]

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

2. (Law) Retaliation.
   --Wharton.

n. (context legal English) An act of retaliation taken by one nation against another as a reprisal

Retorsion (from , from , influenced by Late Latin, 1585–95, torsi, a twisting, wringing), a phrase used in international law, is an act perpetrated by one nation upon another in retaliation or reprisal for a similar act perpetrated by the other nation. The typical methods of retorsion are the use of comparably severe measures against citizens of the foreign nation found within the borders of the retaliating nation. It is different from a reprisal in that the retorsion is always an action in conformity with international law, though unmistakably an unfriendly one. Examples include international trade, where disputes within the World Trade Organization are typically tackled in this manner, if dispute settlement does not reach its goal.

Retorsion also signifies the act by which an individual returns to his adversary evil for evil.