n. In Australia, any one of several species of grasses having stiff, sharp-pointed leaves or spiny flower-clusters, especially the two following, distantly related species: Spinifex hirsutus, the hairy spinifex or spiny rolling-grass. See under rolling-grass.n. Triodia irritans, the desert spinifex, more often called porcupine-grass. See porcupine-grass, 2.