pileus /ˈpɪliəs/ noun5 •(historical) A conical felt hat worn in Ancient Rome and Greece.Among the Romans the cap of felt was the emblem of liberty. When a slave obtained his freedom he had his head shaved, and wore instead of his hair an undyed pileus. — 1859 •The cap of a mushroom.The stem is easily separable from the pileus at its junction, in this respect being similar to Amanita, Amanitopsis, Lepiota and others. — 1903 •A small thin cloud attached to a cumulus cloud.The most short-lived of all the accessory clouds, pileus is also the most beautiful. — 2011 •The top of the head of a bird, from the bill to the nape. •The bell of a jellyfish. formspilei
