Melicope volcanica is a tree that grows 3–11 m tall, with new growth densely covered in yellowish-brown appressed hirtellous hairs that may become glabrate over time. The leaves are simple and opposite, with blades that vary in shape from elliptic, oblong-elliptic, oblong-ovate, elliptic-ovate, to oblong-obovate, measuring 3–18(–25) cm long and 1.5–3(–14.5) cm wide. The apex of the leaves ranges from rounded to obtuse and sometimes emarginate, or occasionally acute and minutely acuminate, while the base is cuneate or rounded and weakly emarginate. The upper surfaces are either glabrous or have a short-hirtellous midrib, and the lower surfaces are sparsely short-hirtellous but often become glabrate; the midrib is variably short-hirtellous, sometimes puberulent or glabrate, and the blades are coriaceous. The margins of the leaves are entire, and the primary lateral veins are prominent, usually numbering 10–20 pairs, with an arched vein 1–5 mm from the margin. The venation is pinnate with lateral veins connected by an arched submarginal vein, forming a detailed reticulate pattern. The petioles range from 7–56 mm long, are short-hirtellous to glabrate, and have no stipules. The flowers appear in groups of 1–5(–11) within axillary cymes extending up to 6 cm, featuring peduncles 7–38 mm long and pedicels 5–20 mm long that are slightly clavate just below the calyx. The calyx is composed of 4 imbricate sepals; in staminate flowers, the sepals are deltate, 2.5–4 mm long, and puberulent, often densely so, while in pistillate flowers, the sepals are ovate, 2.5–3 mm long, and puberulent. The corolla consists of 4 valvate petals; in staminate flowers, the petals are narrowly deltate, 6–8 mm long, either puberulent or glabrous, and in pistillate flowers, the petals are deltate, approximately 6 mm long, and can be either puberulent or glabrous. There are eight stamens arranged in two whorls, distinct and always present in functionally pistillate flowers. The superior ovary in pistillate flowers is 4-celled and lobed; the carpels are connate and slightly distinct at the apex to almost entirely distinct and densely covered in yellowish-brown tomentellous hairs. Each cell contains 2 hemitropous, ascending ovules. The style is short, hirtellous, approximately 2.5–3 mm long, and terminates in 4 short stigmatic branches, while in staminate flowers, the ovary is densely tomentulose with a style about 1.2 mm long. The fruits are capsules that measure (16–)25–40(–50) mm wide and consist of carpels that are connate ¼–⅓ their length, measuring (8–)12–24 mm long. The carpels may be straight or somewhat reflexed, with an exocarp that is finely puberulent, especially around the base, sometimes nearly glabrate, and an endocarp that is glabrous or sparsely puberulent, usually only near the suture. The carpels dehisce along the upper suture. The seeds, usually 2 per carpel, measure 8–10 mm long, are glossy black when ripe, crustaceous, ovoid, and sometimes angled from compression. The embryo is straight, within fleshy endosperm, with a short radicle and compressed, ovate cotyledons. The putamen is brown and warty. It inhabits mesic to wet forests between 610 – 2,060 meters.