The term entheogen comes from the Greek words en (within), theos (god), and generare (to generate, to bring forth). It translates as 'becoming divine within'. The term entheogen refers to a " hallucinogen or other psychoactive substance believed to occasion a spiritual or " mystical experience, similar to those in traditional shamanic rituals. The term entheogen was introduced in or shortly before 1979 by the American classical scholars Carl Anton Paul Ruck (b. 1935) et al. as an alternative for terms such as " hallucinogen, "phantasticum, "eideticum, psychotic, and "psychedelic. The reason for coining this neologism was the authors' dissatisfaction with the usual connotations of the latter terms, especially in contradistinction to the shaman's striving for "transcendent and beatific states of communion with deity". As Ruck et al. state, it would be "incongruous to speak of a shaman's taking a 'psychedelic' drug." Some examples of traditional entheogens are ayahuasca, cannabis, ibogaine, kava, opium, psilocybin mushrooms, peyote, salvia, and tobacco. Today a person intentionally employing an entheogen for the purpose of exploring the psyche may be called a " psychonaut.
References
Ruck, C.A.P., Bigwood, J., Staples, R., Wasson, R.G., Ott, J. (1979). Entheogens. Journal of Psychedelic Drugs, 11, 145-146.
Dictionary of Hallucinations. J.D. Blom. 2010.