1. A pseudoscientific predecessor of chemistry; sought to turn base metals into gold
2. A power like that claimed by alchemists
Since its apparent origin in ancient Egypt, alchemy, both a science and a spiritual discipline, had spread far across the world. Many were not just ancient chemists but were said to follow the 'Great Work', or God's purpose for mankind; possibly to harvest spiritual perfection from the chaff of imperfection and sin.
Ironically, the art of alchemy was lost a short time after more modern systems of physics and chemistry were theorised by the greatest (that is, the greatest out of those confirmed to have existed) alchemist since Paracelsus (many would even say better), Sir Isaac Newton.
However, the ancient spark of alchemy still burns today, albeit much smaller. Those who believe in the power of alchemy, whether practical or spiritual, still study the ancient wisdom of alchemical masters past, and share new information that comes to light (www.alchemyforums.com =P).
One paricular group with strong ties to alchemy are the Rosicrucians. They are a Christian secret society that apparently continue to this day. We don't know a great deal more about them since all initiates swear a solemn oath of secrecy. Do they protect the ancient wisdom of alchemy to this day? It's likely that none of us may ever really know...