Psychedelic is a term coined by Humphrey Osmond in 1957 and literally means "mind manifesting." During the fifties and sixties, scientific investigation of the positive therapeutic and spiritual benefits of LSD (the most popular psychedelic of the '60s), proliferated. This was followed by widespread popularization of the drug by the "high priest" of drug culture, Timothy Leary. Popularization was followed by a paranoid societal backlash which led to fierce legislative prohibitions against the ingestion of LSD.
In order to sidestep the negative press and unreasonable social paranoia of substances that otherwise demonstrated remarkable therapeutic potential (Sharp, 2008), Ruck, Bigwood, Staples, Ott, and Wasson (1979) replaced the term psychedelic with entheogen (literally "becoming the God within"). Entheogens such as LSD, Psilocybin, Peyote, and other psychedelic substances are a powerful class of Crown Activators which can be used to facilitate the activation and awakening of the Crown Chakra.
Ruck, Carl A.P., Bigwood, Jeremy., Staples, Danny., Ott, Jonathan & Wasson, R.Gordon. (1970). Entheogens. Journal of Psychedelic Drugs. 1: 145-6. http://www.entheomedia.org/entheogen.htm
Sharp, Michael (2008). Entheogens. The SpiritWiki: http://www.thespiritwiki.com/index.php/Entheogens [Accessed: March 13, 2008]