The Collaborative International Dictionary of English v.0.48:

Trisplanchnic \Tri*splanch"nic\, a. [Tri- + splanchnic.] (Anat.)
   Of or pertaining to the three great splanchnic cavities,
   namely, that of the head, the chest, and the abdomen; --
   applied to the sympathetic nervous system.
   [1913 Webster]