spinifex noun 2adjective 1forms 3 noun2 •Any of numerous species of grass in genus Spinifex, growing in sand dunes. •(Australia) Any of several spiny grass species of the genus Triodia, endemic to arid outback Australia. adjective1 •Composed of dendritic plates, which present as the scored texture of bundled, spine-like structures typical of komatiites. formsspinifexes · more spinifex · most spinifex