Perennial twining herb. Stems rather slender, somewhat ridged, mostly glabrous, up to c. 3 m long; flowering shoots often leafless. Leaflets 2.2–7.5 × 0.8–3.7 cm, the terminal leaflet rhombic-lanceolate to triangular-ovate, the lateral leaflets similar but markedly asymmetrical, falcate; all leaflets narrowed to a rounded but mucronulate apex, or slightly emarginate, more rarely sharply acute, rounded at the base, with sparse short bristly hairs scattered on upper and lower surfaces and the margins, or glabrescent or more rarely densely pubescent, venation reticulate and prominent on both surfaces; petiole 2–6.5 cm long; rhachis 0.4–1.6 cm long; petiolules c. 2.5 mm long; stipules c. 3 mm long, narrowly ovate-elliptic. Inflorescence axis often much wrinkled, 0.4–1.5 cm long, often 2–3-branched or sometimes peduncle 3–4 cm long; pedicels 0.6–1.4 cm long; bracts and bracteoles minute, c. 1 mm long, ovate, ribbed, ciliate. Calyx tube 3–4 mm long, glabrous; lobes c. 2 mm long, deltate, ciliate, the upper pair united into a low rounded lip. Standard blue, greenish-yellow or mostly mauve, 1.5 × 1.8 cm; wings violet or pink; keel mostly pale. Hairs in a ring around stigma, clearly branched. Pods 7.5–12.5 cm × 5 mm, linear, curved at the tip, glabrous. Seeds dark blackish-red or brown mottled black, 5.5–8 × 3–4 × 2.5–3.2 mm, somewhat keeled along the distil margin, hollowed around the hilum.