Cyanea glabra is a branched shrub with an unknown height, featuring dimorphic leaves where juveniles have pinnately cleft, parted, or divided blades measuring 20–46 cm long and 10–20 cm wide, with 5–8 segments per side. Adult leaves are elliptic to oblanceolate, measuring 23–36 cm in length and 7–12 cm in width. Both juvenile and adult leaves have acuminate apices, with juvenile leaf bases being truncate or obtuse and adult leaf bases obtuse to cuneate. The leaf surfaces display variability, with juveniles having green, glabrous upper surfaces and pale green, glabrous, or sparsely pubescent lower surfaces, often aculeate on the midrib and veins. Adult leaves are similarly colored but are glabrous or sparsely pubescent on the lower surfaces. The margins of juvenile plants are callose–denticulate to callose–dentate, while adult leaves have callose–denticulate to irregularly lobed margins. Juvenile petioles, which are aculeate, measure 9–15 cm, whereas adult petioles are 4–11 cm long and can be smooth or sparsely aculeate. The axillary inflorescences contain 6–8 flowers on peduncles 20–55 mm long. The hypanthium is obconical, 7–10 mm long and 4–5 mm wide, with a calyx with triangular or narrowly oblong lobes. The corolla is zygomorphic (bilaterally symmetric), white, often tinged with pale lilac, 50–60 mm long and 8–9 mm wide, and the tube is curved and dorsally cleft. Stamens alternate with the corolla lobes, forming a staminal column that is glabrous, and the anthers are dithecal, opening by longitudinal slits. The ovary is inferior and 2-celled, with axile placentation and a 2-lobed stigma that becomes receptive after the style grows through the anther tube. The fruit is an ellipsoid, yellowish-orange berry, 10–15 mm long, with numerous small, smooth, shiny seeds, ca. 0.4–0.5(–2) mm long, with a straight, short to spatulate dicotyledonous embryo embedded in oily endosperm. It occurs in wet forests at elevations between 975-1,340 meters.