Mucuna gigantea subsp. gigantea is a large, woody liana. The stems are high-climbing or sprawling, ranging from 8–15(–80) meters long. The leaves are compound and alternate. The leaflets are broadly elliptic or ovate, measuring 4–13 cm long and 2.5–7.5 cm wide, with the lateral leaflets being asymmetrical. The surfaces are glabrous or glabrate, and the leaflet margins are entire. Leaves are petiolate, with caducous stipules, and the leaflets have stipels. The flowers are arranged in short, corymbose pseudoracemes, which are pendulous on long peduncles. Bracts and bracteoles are fugacious, with bracts up to 7 mm long and bracteoles up to 14 mm long. The flowers are papilionaceous (pea-like) with a campanulate (bell-shaped) bilabiate calyx. The calyx lobes are deltate, 2–4 mm long. The corolla is yellowish green, 3–4.5 cm long, and showy, with the standard petal being shorter than the other petals. The wings are incurved and stiffened at the apex, while the keel is angularly curved upward. There are 10 stamens; the upper stamen is distinct, while the other 9 are connate into a tube. The anthers are dimorphic, with 5 larger, subbasifixed anthers alternating with 5 shorter ones. The ovary is superior, with few ovules, and the style is apical, filiform, and glabrous apically. The stigma is small and terminal. The pods (fruit) are compressed, measuring (7–)10–15 cm long and 3–5(–6) cm wide. They are covered with stiff, irritating, orangish-brown hairs but quickly become glabrate. The faces of the pods are pitted and reticulate, without transverse lamellae. The seeds are brown, brown mottled with black, or rarely entirely black. They are discoid, 2–3 cm long, and 1.8–2.5 cm wide, with the hilum extending over ¾ to 5/6 of the circumference. It sprawls over rocks, shrubs, and trees, usually near the ocean or streams between 0–310 meters.