Geniostoma lorencianum is a small tree reaching heights of 3–4 meters. The trunk, about 3–7 cm in diameter at the base, exhibits grayish-brown bark mottled with white or dark brown. Its stems are terete (cylindrical), and its lateral branches are dichotomously branched. Young stems are densely tomentose, becoming glabrate as they age. The leaves of this species are simple and opposite, with elliptic blades–ovate or elliptic-lanceolate in juveniles, measuring between (5.52)7.5–12(216) by (1.82)3–5.5(27) cm. They are chartaceous and membranous with an acuminate, slightly falcate apex and deeply cordate to auriculate base. The upper surfaces are medium green and become hirsute to puberulent upon maturity, while the lower surfaces start densely tomentose and maintain this density. The leaves feature entire margins and are pinnately veined. Petioles are (1.32)1.9–3.7 cm long, and stipules are interpetiolar, hirsute to tomentose, forming a truncate sheath 1.5–2 mm long and often splits with age. It produces terminal, open corymbiform cyme inflorescences with 3–11 flowers in pistillate and 15–34 in staminate plants. Peduncles and pedicels are puberulent, with the former measuring 20–42 mm (elongating to 60 mm in fruit) and the latter 13–32 mm (elongating to 40 mm in fruit). Bracts and bracteoles are linear subulate, measuring 1.4–2.4 mm by 0.4 mm. Flowers are functionally unisexual, and the plant is dioecious. Calyx lobes are 5–6, puberulent, ovate–deltate, and measure 2.0–2.7 mm by 0.9–1.3 mm. The corolla is narrowly urceolate, green, fleshy, and puberulent, measuring 11.5–15 mm in staminate flowers. Staminate flowers have 5–6 stamens, slightly exerted, with dorsifixed anthers. The female ovary in male flowers is hirtellous. The fruits are lanceoloid to ovoid capsules, green transitioning to brown upon maturing, measuring 25–37 mm long, with valves longitudinally striate and not keeled. Seeds are ± winged, numerous, ellipsoid to ovoid–ellipsoid, measuring 2.5–2.9 mm by 1.3–1.6 mm, with a minutely papillose to areolate surface and embedded in orange to red pulp. It grows in montane mixed mesic forests at an elevation of approximately 1,160 meters.