Phyllodium is a genus of flowering plants in the legume family, Fabaceae. It belongs to the subfamily Faboideae. ...
• (n.) A petiole dilated into the form of a blade, and usually with vertical edges, as in the Australian acacias.
Phyl·lo'di·um noun ; plural Phyllodia . [ New Latin , from Greek ... leaflike; ... leaf + ... form.] (Botany) A petiole dilated into the form of a blade, and usually with vertical edges, as in the Australian acacias. 
Leaf-like petiole and no blade, as in some acacias and other plants.