The Collaborative International Dictionary of English v.0.48:

Tripinnatifid \Tri`pin*nat"i*fid\, a. [Pref. tri- + pinnatifid.]
   (Bot.)
   Thrice pinnately cleft; -- said of a pinnatifid leaf when its
   segments are pinnatifid, and the subdivisions of these also
   are pinnatifid.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tripinnatifid
    adj 1: (of a leaf shape) bipinnatifid with segments pinnatifid