pileus

/P AY1 L AH0 S/
noun
  1. 1

    The cap of a mushroom.

  2. 2

    The bell of a jellyfish.

  3. 3

    A small thin cloud attached to a cumulus cloud.

  4. 4

    A conical felt hat worn in Ancient Rome and Greece.

  5. 5

    The top of the head of a bird, from the bill to the nape.

    syn:crown

Source: https://en.wiktionary.org/wiki/pileus