The Collaborative International Dictionary of English v.0.48:

Spinifex \Spin"i*fex\, n. [NL.; L. spina spine + facere to
   make.]
   1. (Bot.) A genus of chiefly Australian grasses, the seeds of
      which bear an elastic spine. Spinifex hirsutus (black
      grass) and Spinifex longifolius are useful as sand
      binders. Spinifex paradoxusis a valuable perennial
      fodder plant. Also, a plant of this genus.
      [Webster 1913 Suppl.]

   2. Any of several Australian grasses of the genus
      Tricuspis, which often form dense, almost impassable
      growth, their leaves being stiff and sharp-pointed.
      [Webster 1913 Suppl.]