Acacia crassiuscula is an erect, often spindly shrub that typically grows to a height of and has
glabrous branchlets. Its phyllodes are ascending to erect, linear, straight to slightly curved, long and wide, somewhat rigid, dark green, glabrous and more or less sharply pointed. The midrib of the phyllode is rather prominent, and there is a
gland from the base of the phyllode. The flowers are borne in three to eight spherical heads in
racemes long. The heads are on a
pedicel long, each head long with 13 to 20 cream-coloured flowers. Flowering occurs from about May to October, and the pods are linear, thinly leathery and glabrous, up to long and wide and shallowly constricted between the seeds. The seeds are oblong to elliptic, long, semi glossy and black with a thick
aril on the end. ==Taxonomy==