The Collaborative International Dictionary of English v.0.48:

Trinervate \Tri*nerv"ate\, a. [NL. trinervatus; pref. tri- + L.
   nervus nerve.] (Bot.)
   Having three ribs or nerves extending unbranched from the
   base to the apex; -- said of a leaf. --Gray.
   [1913 Webster] Trinerve