Melicope rostrata is an erect palmoid shrub that typically reaches 1–3 meters high. The main stem, with a 1–2 cm diameter, is few-branched, with branches ascending and leafy toward the apex. The new growth is hirtellous when freshly broken, and the wood emits a pepsin-like odor. The leaves are simple and opposite, with narrowly oblong blades to very narrowly elliptic or sub-spatulate, usually measuring 20–42 cm long and 4–12 cm wide. The leaf apex ranges from bluntly acute to sub-acuminate or rounded, while the base is truncate, obtuse, or rarely subcordate. The surfaces are glabrate, and the margins are entire. The lateral veins are numerous, almost perpendicular to the midrib, and connected by a deeply arched vein. The midrib is sulcate on the upper surface of the leaf. Petioles are 3–18 mm long, and it lacks stipules. The flowers occur in axillary cymes that are hirtellous and sometimes clustered in fascicles up to 2 cm long, located in the leaf axils or below the leaves. The peduncles are 1–3 mm long, and the pedicels are 4–9 mm long. Flowers are bisexual (perfect) and actinomorphic (radially symmetric), featuring a calyx of 4 sepals in imbricated pairs, broadly ovate, about 3 mm long and 5 mm wide, and sparsely puberulent. The corolla comprises four white or cream petals, slightly imbricate, oblong, 12–13 mm long and approximately 5 mm wide, and glabrous. The plant has eight stamens with white filaments nearly completely connate into a staminal tube; the anthers are subsessile, elongate, and dithecal. The superior ovary is 4-carpellate and 4-lobed, with carpels connate in the lower half and forming a subconical structure narrowing into a short style; placentation is axile with 5–8 ovules per carpel, pendulous on short, broad funiculi. The style is columnar, and the stigmas are linear, erect, connate, and slightly thickened apically. The fruit is cruciate, measuring approximately 20–25 mm in diameter across the carpel apices, and is glabrous. The carpels, erect to somewhat spreading in fruit, are about 12–17 mm long and topped with a long slender beak measuring 5–10 mm. Each carpel contains eight seeds, with the embryo embedded in white endosperm. The fruit has thin, broad, rounded cotyledons and short hypocotyl. It grows in mesic forests and valleys between 760 – 1,220 meters.