The cap of C. variegata is thin, initially oval-shaped then bell-shaped, and then flattened with the margin turned upward; it reaches diameters of up to 12 in (30.5 cm). When young, the surface of the cap is covered with a woolly whitish or yellowish veil that breaks up into short-lived flakes or scales; this process reveals the radially striate (grooved) gray to grayish-brown cap surface. The gills are broad, thin, crowded closely together, and free from attachment to the stem. They are initially white but turn to dark purplish-brown as the spores mature. The stem is 4 to 12 in (10.2 to 30.5 cm) and up to 1 cm (0.4 in) thick, hollow, and whitish. It is roughly the same width throughout the length of the stem, and may have a wispy, cotton-like ring present near the base. Clusters of fruit bodies have a mass of rhizomorphs at the base called an ozonium. In deposit, the spores are dark brown. A light microscope may be used to reveal more features of the spores, including smooth surfaces, a dark brown color, an ellipsoid shape in face view and an egg shape in side view, and dimensions of 7.5–9.5 by 4–4.5 µm. The apex of the spore appears truncated because of the presence of a germ pore. The basidia (spore-bearing cells) are hyaline (translucent), with dimensions of 14–16 by 6.5–7.5 µm. The paraphyses are 9–11 by 8–10 µm, hyaline, and collapse readily. The pleurocystidia (cystidia present on the gill face) are abundant, roughly cylindrical, hyaline, and measure 100–150 by 20–35 µm. Cheilocystidia (cystidia on the edge of an gill) are present in young specimens, and are roughly ellipsoid, measuring 50–80 by 15–25 µm. Clamp connections are abundant in the hyphae in all tissues through the fruit body. The edibility of Coprinopsis variegata has not been clearly established, and opinions differ as to its desirability. One 1987 field guide to North American species warns against consumption, calling it "not recommended", a conclusion shared in a 2006 field guide to Pennsylvanian and mid-Atlantic mushrooms, but not before describing it as "the best of the inky caps, with a richer flavor and better texture than the famous shaggy mane". The bitter-tasting mushroom is not considered poisonous. However, the fruit bodies are suspected to contain the Antabuse-like chemical coprine, which causes a poisoning reaction when consumed with alcohol. Additionally, cases of allergic reactions against extracts from mushroom tissues have been reported in skin tests.
