Trifoliate

from WordNet (r) 3.0 (2006)

trifoliate
    adj 1: (of a leaf shape) having three leaflets [syn:
           {trifoliate}, {trifoliolate}, {trifoliated}]

from The Collaborative International Dictionary of English v.0.48

Trifoliate \Tri*fo"li*ate\, Trifoliated \Tri*fo"li*a`ted\, a.
   [Tri- + foliate. Cf. {Trefoil}.] (Bot.)
   Having three leaves or leaflets, as clover. See Illust. of
   {Shamrock}.
   [1913 Webster]