The Collaborative International Dictionary of English v.0.48:

Trinodal \Tri*nod"al\, a. [L. trinodis three-knotted; tri- (see
   Tri-) + nodus knot.]
   1. (Bot.) Having three knots or nodes; having three points
      from which a leaf may shoot; as, a trinodal stem.
      [1913 Webster]

   2. (Geom.) Having three nodal points.
      [1913 Webster]