Source : Webster's Revised Unabridged Dictionary (1913)

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}.

Source : WordNet®

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