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 paradoxus}is 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.]