Noun, pl. pallia or palliums
1. (Zoology) The mantle of a mollusc (wiktionary.org); the mantle of a bird (merriam-webster.com); a protective layer of epidermis in mollusks or brachiopods that secretes a substance forming the shell) (wordnetweb.princeton.edu).
2. (Meteorology) A sheet of cloud covering the whole sky, especially nimbostratus. (wiktionary.org)
3. (Anatomy) The cerebral cortex (wiktionary.org); the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum) (wordnetweb.princeton.edu).
4. A large, square, woolen cloak which enveloped the whole person, worn by the Greeks and by certain Romans. It is the Roman name of a Greek garment (biology-online.org); a draped rectangular cloth worn as a cloak by men of ancient Greece and Rome(merriam-webster.com). A white woolen band with pendants in front and back worn over the chasuble by a pope or archbishop as a symbol of full episcopal authority (merriam-webster.com).