The Collaborative International Dictionary of English v.0.48:

Triplication \Trip"li*ca"tion\, n. [L. triplicatio: cf. F.
   triplication.]
   1. The act of tripling, or making threefold, or adding three
      together. --Glanvill.
      [1913 Webster]

   2. (Civil Law) Same as Surrejoinder.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

TRIPLICATION, pleading. This was formerly used in pleading instead of
rebutter. 1 Bro. Civ. Law, 469, n.