The terms "entheogen" and "entheogenic" were coined and popularized by Jonathan Ott to describe the various chemicals that enhance or alter awareness.
Entheogenic use of a mind-altering substance occurs when it is used in an attempt to contact the divine in or around us or, indeed, to help the user himself or herself reach a state of divinity.
"But to those who felt that sacramental input outweighed the psychiatric input, the term "Entheogens" was more attractive. The existence of God within us. "En" inside, and "Theo" God, and "Gen" which is short for genesis, origin or creation. But existence is not creation. A fantastic new drug might reveal that there is a God there inside of us. But that drug does not create that God within us." &mdash Alexander Shulgin
Substances in common entheogenic use include cannabis, LSD, ketamine, Salvia Divinorum, psilocybin, nitrous oxide, mescaline and the phenethylamines and tryptamines you can read about in Shulgin's PIHKAL and TIHKAL.