|pileus (pī'lē-əs) Pronunciation Key
Plural pilei (pī'lē-ī')
The umbrellalike fruiting structure forming the top of a fleshy fungus. It is supported by the stipe. The cap of a mushroom is a pileus.
close-fitting, brimless hat worn by the ancient Romans and copied from the Greek sailor's hat called the pilos. In Roman times the head was generally left uncovered, but commoners and freed slaves sometimes wore the felt pileus
Learn more about pileus with a free trial on Britannica.com.