Entheogen[ic] from entheos meaning becoming the divine within is derived from the same root word that is cognate with the word enthusiasm. Entheogen is now considered the primary term for shamanic inebriants. Entheogen is an attempt to describe all the modalities of a divine inebriant. Additionally the term psychedelic is perceived as a pejorative outside counter-culture. Thus an entheogen is a psychedelic substance used in ritual context.
Despite Western civilization’s rather recent awareness, hallucinogenic sacramental plant use has been a part of the human experience for millennia. Indeed, a desire for a sacred altered state of consciousness seems to be part of how we define ourselves as human. The altered state of consciousness being highly desired for spiritual and healing purposes --- is shamanic in nature.
Shamanism was the Paleolithic spiritual practice of healing, divination and art developed some ten to fifty thousand years ago. It was not so much a religion as it was a set of techniques. The most important shamanic technique, whether the practioners lived in Siberia or in the Amazon, was Ekstasis or ecstasy -- meaning the flight of the soul from the body. And the most important way of achieving this ecstasy was through the use of psychedelics plants or entheogens.