Final answer:
An alchemist is a practitioner of alchemy, who was part medieval scientist, part philosopher, and engaged in early forms of chemical experimentation and theory, including the effort to transmute base metals into gold and discover an elixir of life.
Step-by-step explanation:
An alchemist can be defined as a practitioner of alchemy, whose work blended elements of chemistry, physics, philosophy, astrology, and spirituality. In a broader sense, it is someone engaged in the medieval predecessor to modern chemistry, mainly focused on the transmutation of substances (such as converting lead into gold) and the discovery of a panacea or the elixir of life. Alchemists, therefore, were part medieval scientist, part philosopher, and they applied a range of practices that can be considered proto-scientific. Over time, as the field of alchemy evolved into the science of chemistry, the secretive and mystical aspects of alchemy were abandoned, leading to more methodical and empirical scientific approaches, as exemplified by later chemists. The contributions of historical alchemists paved the way for significant advancements in understanding the properties and reactions of substances, leading to the modern field of chemical science.