Someone who explores consciousness, the mind, and "inner space" through the use of meditation, drugs, sensory deprivation, and other methods.

A psychonaut (from the Greek ψυχοναύτης, meaning literally a sailor of the psyche) is a person who uses trance technologies from any of the world's religions, modern psychology, and other assorted paradigms, to explore the psyche, their own consciousness, and potentially improve real performance of certain psychological tasks. The term is often associated with the use of hallucinogens or entheogens as guides, or means, to achieve inward spiritual experiences. This is quite distinct from religious use, or social and leisure use of drugs, although invariably these overlap.