The Collaborative International Dictionary of English v.0.48:

Trilobed \Tri"lobed\, a. [Pref. tri- + lobe.]
   Same as Trilobate.
   [1913 Webster]

WordNet (r) 3.0 (2006):

trilobed
    adj 1: (of a leaf shape) divided into three lobes [syn:
           trilobate, trilobated, trilobed, three-lobed]