pileus

American  

[pahy-lee-uhs, pil-ee-] / ˈpaɪ li əs, ˈpɪl i- /

noun

plural

pilei, pileus

1. Mycology. the horizontal portion of a mushroom, bearing gills, tubes, etc., on its underside; a cap.

2. Zoology.

   1. the umbrella or bell of a jellyfish.

   2. pileum.

3. Also called cap cloud.  Also called scarf cloud.  Meteorology. a small, thin cloud just above or attached to a growing cumulus cloud.

4. a felt skullcap worn by the ancient Romans and Greeks.

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pileus British  

/ ˈpɪl-, ˈpaɪlɪəs /

noun

1. the upper cap-shaped part of a mushroom or similar spore-producing body

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pileus Scientific  

/ pī′lē-əs /

plural

pilei

1. 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.

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Etymology

Origin of pileus

1750–60; < New Latin, special use of Latin pīleus skullcap; akin to Greek pîlos felt, felt cap

Example Sentences

This species is unique for the dorsal attachment of its stipe to the top of the pileus, and the abundant cystidia covering all surfaces of the fruiting body.

From Salon • Apr. 26, 2025

The reverse features two daggers on either side of a cap known as a pileus.

From New York Times • Mar. 22, 2023

A cumulus, for example, might just be a cumulus; or it might be a cumulus fractus, if its edges are tattered; or a cumulus pileus, if a smaller cloud appears over it like a hood.

From New York Times • May 4, 2016

Cardineo fulgens ego honore, et Episcopus ecce Mors manet ecce omnes, Phrygeus quos pileus ornat.

From The Dance of Death Exhibited in Elegant Engravings on Wood with a Dissertation on the Several Representations of that Subject but More Particularly on Those Ascribed to Macaber and Hans Holbein by Douce, Francis

Stem cartilaginous; pileus convexo-plane, edge incurved at first; gills soon separating from stem.

From European Fungus Flora: Agaricaceae by Massee, George