The Collaborative International Dictionary of English v.0.48:

Three-lobed \Three"-lobed`\, a.
   Having three lobes.
   [1913 Webster]

   Three-lobed leaf (Bot.), a leaf divided into three parts,
      the sinuses extending not more than half way to the
      middle, and either the parts of the sinuses being rounded.
      [1913 Webster]

WordNet (r) 3.0 (2006):

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