1. A medieval chemical philosophy having as its asserted aims the transmutation of base metals into gold, the discovery of the panacea, and the preparation of the elixir of longevity.
2. A seemingly magical power or process of transmuting: "He wondered by what alchemy it was changed, so that what sickened him one hour, maddened him with hunger the next" (Marjorie K. Rawlings).
[Middle English alkamie, from Old French alquemie, from Medieval Latin alchymia, from Arabic al-kmiy' : al-, the + kmiy', chemistry (from Late Greek khmeia, khumeia, perhaps from Greek Khmia, Egypt).]