Pseudolithos cubiformis exhibits a unique appearance as it grows into a large, granite grey cube, though it can vary in shape, color, and size. Typically, it boasts a single-stemmed structure with a cube-like form and tuberculate, leathery skin. The coloration varies from light green in shaded conditions to olive/grey/green in partial sun or reddish-brown in full sun. This species produces clusters of flowers with greyish-green hairy petals and a purple center, notable for being the largest in the genus and emitting an odor reminiscent of rotting meat to attract fly pollinators. Pseudolithos cubiformis typically blooms in late summer on the lower side of the plants, but flowering can occur throughout the year under suitable growing conditions.