Ambergris is a solid, waxy, flammable substance of a dull gray or blackish color produced in the digestive system of and regurgitated or secreted by sperm whales. Chunks of it have been known to sell for tens of thousands of dollars.
The principal historical use of ambergris was as a fixative in perfumery, though it has now been largely displaced by synthetics.
Freshly produced ambergris has a marine, fecal odor. However, as it ages, it acquires a sweet, earthy scent commonly likened to the fragrance of rubbing alcohol. The beaks of giant squid can commonly be found in these hardened masses, suggesting that the ambergris is a secreted substance in the intestines of the whales which protects it from rips and tears from the pointed beaks.
Ancient Egyptians burned ambergris as incense, while in modern Egypt ambergris is used for scenting cigarettes. The ancient Chinese called the substance “dragon’s spittle fragrance”. During the Black Death in Europe, people believed that carrying a ball of ambergris could help prevent them from getting the plague. This was because the fragrance covered the smell of the air which was believed to be the cause of plague.
This substance has also been used historically as a flavoring for food, and some people consider it an aphrodisiac. During the Middle Ages, Europeans used ambergris as a medication for headaches, colds, epilepsy, and other ailments.
[Via Wikipedia, Scientific American]