Plants perennial with slender rhizomes; culms in fascicles, up to 1 m long, erect or scandent, slender, wiry, with many nodes. Leaf blades 3-10.5 cm long, 2-7 mm wide, narrowly lanceolate, widely diverging to slightly reflexed, acute. Panicles 6-25 cm long, narrowly elliptic tot narrowly blong, the central axes bearing numerous, racemosely arranged, spikelike branches; branches 2-5 cm long, straight or slighly flexuous. Spikelets 1.6-2.4 mm long, wtih 1 floret; glumes equaling the floret, narrow, acuminate; lower glumes slightly falcate; lemmas 1.7-2.1 mm long, elliptic, appressed pilose ver the veins. Caryopses narrowly ellipsoid, trigonous, deeply sulcate on the hilar side.
Trigonochloa rupestris grows on rocky hillsides in the shade f dhrubs and small trees, often straggling through low vegetation, at 100-1800 m. Its range includes southern Ethiopia, Somaliland, Uganda, Kenya, and Yemen.