Eragrostis paupera is a perennial grass with densely tufted, tough, stiff, and strictly erect culms that grow up to 20 cm tall. These culms are sharply scabrous and almost entirely covered by leaf sheaths. The leaves are simple and alternate, with blades up to 5 cm long but typically shorter, hispid on the upper surfaces and slightly scabrous on the lower surfaces, strongly involute when dry. The leaf sheaths are glabrous with prominent, bristly auricles, and the ligule consists of a band of stiff bristles approximately 0.6 mm long. The inflorescence is paniculate, weakly branched, racemose, and sharply scabrous, with few to around 40 spikelets that are straight to somewhat falcate, 5-45 mm long and flattened, measuring 1-2 mm in width. The glumes are membranous, strongly keeled, with a rounded or slightly emarginate apex, with the first approximately 1.5 mm long and the second about 2 mm long. The lemmas are imbricate, concealing the rachilla, appressed, and spread slightly with age, approximately 1.8 mm long, strongly keeled, 3-nerved, with a sharply scabrous keel above and glabrous elsewhere, with hyaline margins and an emarginate apex. The palea is oblong, bent outward, about 1.5 mm long, persistent, with hyaline, thickened, hispid-ciliate margins, and a truncate apex. The fruit is a golden-brown caryopsis, somewhat flattened, subglobose to ovoid, 0.5-0.6 mm long and 0.4-0.6 mm wide. It has a small brown tubercle at the base on the adaxial surface and a convex abaxial surface with a somewhat divided depression in the lower half. It grows on coral sand, gravel, and saline flats in coastal areas at less than 50 meters in elevation.