The Collaborative International Dictionary of English v.0.48:

Phyllodium \Phyl*lo"di*um\, n.; pl. Phyllodia. [NL., fr. Gr. ?
   leaflike; fy`llon leaf + e'i^dos form.] (Bot.)
   A petiole dilated into the form of a blade, and usually with
   vertical edges, as in the Australian acacias.
   [1913 Webster]