carbuncle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A painful localized bacterial infection of the skin and subcutaneous tissue that usually has several openings through which pus is discharged.
• noun A red precious stone, especially a deep-red garnet cut as a cabochon.
• noun A mythical gemstone said to emit light even in total darkness.

from The Century Dictionary.

• noun A beautiful gem of a deep-red color, inclining to scarlet, found chiefly in the East Indies.
• noun In pathology, a circumscribed inflammation of the subcutaneous connective tissue, resulting in suppuration and sloughing, and having a tendency to extend itself, undermining the skin. It is somewhat similar to a boil, but more serious in its effects.
• noun In her.: A charge or bearing generally consisting of 8 radiating staffs or scepters, 4 of which are vertical and horizontal and 4 diagonal or saltierwise, and supposed to represent the precious stone carbuncle. Also called escarbuncle.
• noun The tincture red, when describing a nobleman's escutcheon according to the system of blazoning by precious stones. See blazon, n., 2.
• noun A whelk or “toddy-blossom” on a drunkard's face.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Min.) A beautiful gem of a deep red color (with a mixture of scarlet) called by the Greeks anthrax; found in the East Indies. When held up to the sun, it loses its deep tinge, and becomes of the color of burning coal. The name belongs for the most part to ruby sapphire, though it has been also given to red spinel and garnet.
• noun (Med.) A very painful acute local inflammation of the subcutaneous tissue, esp. of the trunk or back of the neck, characterized by brawny hardness of the affected parts, sloughing of the skin and deeper tissues, and marked constitutional depression. It differs from a boil in size, tendency to spread, and the absence of a central core, and is frequently fatal. It is also called anthrax.
• noun (Her.) A charge or bearing supposed to represent the precious stone. It has eight scepters or staves radiating from a common center. Called also escarbuncle.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun archaic A deep-red or fiery colored garnet or other dark red precious stone, especially when cut cabochon.
• noun An abscess larger than a boil, usually with one or more openings draining pus onto the skin. It is usually caused by bacterial infection.
• noun heraldry A charge or bearing supposed to represent the precious stone, with eight sceptres or staves radiating from a common centre; an escarbuncle.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun deep-red cabochon garnet cut without facets
• noun an infection larger than a boil and with several openings for discharge of pus