[ pahy-lee-uhs, pil-ee- ]

noun,plural pi·le·i [pahy-lee-ahy, pil-ee-ahy] /ˈpaɪ liˌaɪ, ˈpɪl iˌaɪ/ for 1, 2, 4, pi·le·us for 3.
  1. Mycology. the horizontal portion of a mushroom, bearing gills, tubes, etc., on its underside; a cap.

  2. Zoology.

    • the umbrella or bell of a jellyfish.

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

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

Origin of pileus

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

Words Nearby pileus

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How to use pileus in a sentence

British Dictionary definitions for pileus


/ (ˈpaɪlɪəs, ˈpɪl-) /

nounplural -lei (-lɪˌaɪ)
  1. the upper cap-shaped part of a mushroom or similar spore-producing body

Origin of pileus

C18 (botanical use): New Latin, from Latin: felt cap

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for pileus


[ lē-əs ]

Plural pilei (lē-ī′)
  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.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.